Fiber Optic Patch Cord

Welcome to Huihong Technologies fiber optic patch cord factory, where precision meets reliability in every strand we produce. As a leading supplier in the industry, we specialize in crafting top-quality fiber optic patch cords and cables tailored to meet the diverse needs of our clients. From LC, SC, ST, E2000, MU, VF45, FC, MT-RJ, CS, to MPO, MTP, SN, SMA, ODVA, TFOCA, ODC, MMC, MDC, and more, we ensure a comprehensive range to suit various applications. Our fiber optic patch cords are engineered to the highest standards, boasting features such as RoHS compliance, LSZH, Riser, Plenum, OFNR, OFNP ratings, and options for simplex or duplex configurations. Whether you require single-mode (8.3/125, 9/125, SM, OS1, OS2) for long-distance transmission or multimode (50/125, 62.5/125, MM, OM1,OM2,OM3,OM4,OM5) for shorter distances, we have you covered. At huihongfiber facility, precision manufacturing meets rigorous quality control measures to guarantee optimal performance and durability, we also have fast delivery of the fiber patch cables. With a commitment to innovation and customer satisfaction, we stand as your trusted partner in the world of fiber optic connectivity. In this article, we are going to give a comprehensive introduction to fiber optic patch cords, including its structure, connector, optical cables, optical fibers, etc.

Fiber Optic Cables Structure for Patch Cord

There are various types of optical cables to meet different application scenarios. The main types of optical cables are cordage cables, distribution cables, breakout cables, waterproof cables, armored cables, messenger cables, ribbon cables, submarine cables, aerospace cables, hybrid cables and composite cables. Among them, the following types are suitable for fiber jumpers.

Cordage- simplex fiber optic cables and duplex fiber optic cables
The simplest optical cable structure, and the most used for making optical fiber jumpers, are cordage cables. There are two types of optical cables, one is the simplex structure, and the other is the duplex structure. The main feature of cordage fiber optic cables is that they have only one fiber/buffer combination in their outer sheath.

Distribution fiber optic cables
A distribution cable is a multi-core optical cable. Usually, a distribution fiber optic cable consists of a non-conductive strength member and a plurality of tight buffered fibers combined in a sheath. Distribution fiber optic patch cords are usually laid between different buildings, generally they have 4 cores, 6 cores, 8 cores, 12 cores, 24 cores, 36 cores, 48 cores, 72 cores, 96 cores and 144 cores. In many cases, these cores are not fully utilized, and some are used as redundant reserves.

Breakout fiber optic cables
The structure of the breakout fiber optic cable is similar to the distribution cable, the difference is that the breakout fiber cable contains multiple sheathed single-core optical cables as its subunits, while the subunits of the distribution cable are tight buffered fibers. The diameter of the breakout cable is Thicker, they are used to connect fiber optic equipment directly rather than through patch panels.

Armored fiber optic cables
Armored fiber optic cables have two common structures, one with the armor located inside the outer sheath, and the other with the armor located in the outermost layer and the sheath inside it. The armored fiber optic cables of Sunrise Photonics are suitable for stainless steel tubes as the armor of the armored fiber optic patch cords, which have excellent tensile strength, compression resistance and anti-rodent bite. We have both indoor and outdoor rated armored fiber optic patch cords, the structure of fiber optic patch cords are single core dual core and multi core.

Ribbon Fiber Optic Cables
Ribbon fiber optic cables are usually used for laying under the carpet. They have a flat structure, generally 8 or 12 cores, and are used to make mpo/mtp fiber optic patch cords. This fiber optic cable contains fiber ribbons, which are Coated optical fibers arranged side by side.

Aerospace fiber optic cables
The core parts of Aerospace fiber optic patch cords are the same as ordinary optical fibers, but their coating, buffer and jacket parts are quite different from ordinary fiber patch cords. Because they are used in aircraft or in space, they must be able to work in extreme temperature environments and be able to withstand a certain amount of vibration and shock.

NEC Standards For Fiber Optic Cables And Raceways

NEC (National Electrical Code) is a type of standard, it is not an organization, NEC is published by NFPA (National Fire Protection Association). The main significance of NEC standard is to avoid possible risks when using electrical facilities. Many customers, especially companies in the United States, adopt the NEC standard and use fiber optic cables and patch cords that meet its standards.

The NEC standard gives detailed guidance when laying optical fibers in buildings. NEC requires that optical cables and optical fiber jumpers must pass a certain fire rating and smoke characteristics. It points out what fire and smoke requirements should be used in different occasions. grade fiber optic products. NEC standards for fiber patch cords can be found in NEC Article 770. Please note that NEC’s standards are updated every 3 years, usually with new content.

The NEC standard divides optical cables into three types. The first is nonconductive, which means that there is no material that can conduct electricity. The second is conductive, the material of this cable contains non-current-carrying conductive members, such as armor, sheath, or strength member. The third is composite, this cable contains optical fibers and current-carrying conductors. Of course, this cable also May contain non-current-carrying conductive members, such as the presence of metal in the sheath and armor.

NEC divides optical cables into different standards according to their conductivity and flammability to reduce possible hazards. Any fiber optic cables or patch cords for indoor use must comply with NEC standards. Any fiber optic cable for outdoor use must be connected to NEC-compliant indoor fiber optic cables or fiber optic patch cords within a distance of 15′ or 50′ by connector/adapter or fusion splicing when it is inserted into an indoor structure.

Optical cables and optical patch cords that comply with NEC standards have their performance verified by UL (underwriters Laboratory), and there must be clear printing on the outer sheath of the optical cable to indicate which standard the design type of the optical cable meets, such as OFN, OFC, OFNR, OFNP, etc. The cable jacket must also be marked with UL. The indoor optical cables and optical fiber jumpers listed in NEC Article 770 are mainly divided into three categories: Plenum fiber optic cable, Riser fiber optic cable and General-purpose fiber optic cable. Plenum cables, whether conductive or not, they can be used in plenum occasions, Plenum fiber optic cables are flame retardant and low smoke. Riser fiber optic cables, whether conductive or not, are used for vertical run in a shaft or from floor to floor. Riser cables have flame retardant requirements. General purpose cables also have certain flame retardancy, but they cannot be used in riser or plenum occasions.

Optical Cable Markings from NEC Table 770.179

Marking	Descriptions
OFNP	Nonconductive optical fiber plenum cable
OFCP	Conductive optical fiber plenum cable
OFNR	Nonconductive optical fiber riser cable
OFCR	Conductive optical fiber riser cable
OFNG	Nonconductive optical fiber general-purpose cable
OFCG	Conductive optical fiber general-purpose cable
OFN	Nonconductive optical fiber general-purpose cable
OFC	Conductive optical fiber general-purpose cable

The outer surface of optical cables and fiber jumpers typically bears various texts describing the optical fiber type, conformity to standards, cable structure, name, fire rating, and other pertinent information. These markings commonly include the manufacturer’s name or brand.

To facilitate the visual identification of fiber core types in optical cables and fiber patch cords, ITA-598-C specifies a set of color codes. These codes enable straightforward differentiation of optical cables utilizing different fiber types. Additionally, for multi-core cables, the colors of cores within the same cable are also specified.

Here are the listing requirements for optical fiber cables and raceways per Article 770.179:

– **Section 770.179 (A):** Types OFNP and OFCP: Cables marked with these designations are suitable for use in plenums, ducts, and similar spaces where environmental air circulates. They possess adequate fire resistance and emit low levels of smoke.

– **Section 770.179 (B):** Types OFNR and OFCR: Cables labeled with these markings are intended for use in vertical shafts or for vertical runs between floors. They exhibit fire-resistant properties capable of containing fire spread between floors.

– **Section 770.179 (C):** Types OFNG and OFCG: Cables identified with these markings are designed for use in spaces not designated as plenums, typically for general use on a single floor. They offer fire resistance.

– **Section 770.179 (D):** Types OFN and OFC: These cables serve the same purposes as OFNG and OFCG cables. OFN and OFC cables are suitable for general use and provide fire resistance.

Fiber Optic Patch Cord Jacket Colors

With the development of the optical communication industry, different connector types were created by different companies at different times. Most of them are not compatible with each other and have their own standards. Connectors types include SC, LC, FC, ST, E-2000, MU, VF45, MTRJ, DIN, D4, SMA, FDDI, ESCON, TFOCA-I, TFOCA-II, TFOCA-III, CS, MPO, MTP,  Many connectors have faded out of the market over time.

Optical fiber is the most ideal carrier for light wave transmission, but sometimes we need to connect one fiber/cable to another, or sometimes we need to disconnect the connection. The role of fiber optic connectors and fiber optic patch cords is here. Optical fiber jumpers are optical cables with connectors added.

The advantage of optical fiber connector over optical fiber fusion splicing is that it can be connected or disconnected at any time, while optical fiber fusion splicing is permanent. By using fiber optic connectors, a piece of fiber can be accurately connected to the fiber in another device, and the optical loss of the link is very small. In the process, the fiber optic connector protects the tiny, fragile fiber within it, precisely aligning the two different lengths of fiber and connecting them so that they can work together. Because the optical fiber is so tiny, it is difficult for us to connect and disconnect the optical fiber directly without a device such as a connector. Therefore, the optical fiber connector and the optical fiber jumper play a vital role in the optical fiber communication network.

Since fiber optic connectors were developed at different times by different companies (and there are still new types of connectors being developed and brought to market), there are many types and shapes. But they all share major structures: ferrule, cap, body and strain relief.

Ferrule:

Ferrule is the core of the fiber optic connector, and its quality determines the quality of the fiber optic connector. The role of Ferrule is to place the fiber in the correct position. There is a hole in the middle of the ferrule to place the optical fiber. Before the fiber is inserted into the ferrule, its coating is stripped.

Different optical fiber connectors have different ferrule materials, there are three main types: ceramic, metal, and plastic. The size of the hole of Ferrule is not necessarily equal to the size of cladding. For example, for 125um coating, the hole size of ferrule is about 124um to 127um. time, it depends on the actual needs.

Ceramic (aluminum oxide and zirconium oxide) is the main material of the ferrule of the optical fiber connector. The ceramic part is hard enough, and its coefficient of thermal expansion (material expands/contracts with temperature changes) is the same as that of the optical fiber. Most of the optical communication connectors are made of ceramics, such as SC, LC, FC, ST, MU, E-2000, etc.

Metal ferrules, usually made of stainless steel, are as strong as ceramics, but they are less dimensionally stable. Commonly used metal ferrule connectors are of the SMA type.

Plastic ferrules are cheaper than both ceramics and metals, but they are neither as strong nor as reliable as the other two materials. In the process of making the optical fiber patch cord, the optical fiber is epoxied into the ferrule with the end protruding slightly beyond the ferrule’s surface. Then the fiber end is trimmed and polished with the ferrule end face to achieve a precise fit. These works are completed in the factory of sunrise photonics, and the fiber patch cords users get are already with well-polished connectors.

Ferrule is placed into the connector body, which is usually made of metal or plastic. For example, FC, ST are metal, SC, LC, MU, E-2000 are plastic. The role of the connector body is to hold the ferrule, the optical fiber inside it and the cable in place, it transfers strain placed on the fiber optic connector to the optical cable instead of the optical fiber inside.

Cap

Cap here not means dust cap, it is the coupling nut, it fits over the connector body and provides a way to secure the connector, the cap usually is a locking mechanism like LC and SC, or a threaded ring like FC, or a snap attachment like the ST. Manufacturers use different methods to secure the strength member of the cable and the connector together, a popular method is to crimping a ring or band around the strength member and secure it to the fiber optic connector’s body. By doing this the tensile stresses placed on the fiber optic connector is passed to the cable’s strength member, so that the connector has the ability to resist tension.

Body

The outer sheath of the optical cable and the connector body are not necessarily fastened, this depends on the fiber connector and patch cord type. When it is necessary to secure the jacket to the connector body, we have two common methods, one is similar to the LC connector, which use a shrink tube to securely fasten the cable jacket and the connector body. Another is similar to the SC connector, using a band or a ring crimped around the cable jacket to secure it to the connector.

Strain Relief

Strain relief is also called boot, it is usually sleeved on the outer skin of the optical cable and is securely connected with the body of the fiber optic connector. The boot is usually made of elastic material but is also strong. Strain relief/boot is very useful, it prevents the fiber optic patch cord from being over bent at the connector point. Different connectors have different industry default strain relief patterns, for example, boots such as SC, LC, FC, ST have a completely different look.

Strain relief also varies according to actual needs, sometimes we need very short strain relief parts, such as for fiber patch cords used in data centers, so sunrise photonics has a series of short boot connectors, especially for SC and LC fibers jumper. In addition, we also have Uniboot LC cables, the Uniboot cable only has a simplex boot for a 2 core LC connector. Sometimes we need a bent boot, we have 45-degree and 90-degree fixed bending angle connector boots, and we also have flex boot connectors that can bend at any angle. The strain relief material is relatively soft and there is a reinforcement inside it, when you bend it to a certain angle, it can be fixed at that angle and won’t get back into shape on its own.

How to join two fiber optic connectors/ fiber optic patch cords

Under normal circumstances, two different optical fiber connectors cannot be directly connected (Such as SC, FC, ST, LC, E-2000, MU, these belong to what we call the general case, the exception is some hermaphroditic fiber connectors, you can directly connect the two connectors without going through additional fiber adapter), and we need a device called fiber optic adapter. Fiber optic adapter is also called alignment sleeve, mating sleeve. Fiber optic adapter defined by ANSI-TIA-568-C is a mechanical device that can align and join two fiber optic connectors and form a fiber optic connection. There are different fiber optic adapters, some can join two same type connectors, such as SC to SC adapter, LC to LC adapter, some can join two different types of connectors, such as SC to LC adapter, SC to ST adapter. The adapter that can join two different types of connectors are called hybrid fiber optic adapters.

Connectors can be joined with adapters, and they can also mate with equipment or device receptacles. We can often see receptacles on equipment like fiber converters, switches, etc. the receptacles can be seen on transmitter side equipment and receiver side equipment, and some passive device also have such receptacles. The receptacles are similar to one-half of the mating sleeves. By using the receptacles, the fiber optic connector can directly plug into it and link to the fiber optic equipment.

Connector Standard

The design purpose of the fiber optic connector is the same, and it is used to align the ends of the two optical fibers and connect and fix them firmly. However, the design of fiber optic connectors varies due to technological advancements and changing needs. Therefore, we can now see that there are a variety of optical fiber connectors on the market, some connectors have gradually faded out of the market, and some newly designed connectors are constantly emerging. It is precisely because there are so many types of connectors that TIA (Telecommunications Industry Association) does not specify industry specifications for connectors. Only in ANSI-TIA-568-C, it specifies the performance standard that connectors need to achieve.

Connector Performance

ANSI/TIA-568-C.3 Appendix A defines performance standards for fiber optic connectors. Whether it is a single-mode or multi-mode connector, the max insertion loss allowed for the mated connectors pair is 0.75dB.

ANSI/TIA-568-C.3 also defines the return loss as the ratio of the outgoing fiber optic signal to the power of the reflected signal. The return loss is also measured by dB. for the multimode, the minimum return loss is 20dB (this means the fiber optic signal energy from the light source transmitting via the fiber interconnection is 20dB greater than the fiber optic signal being reflected by the fiber interconnection to the light source). for single mode, it is minimum 26dB. There is an exception, for CATV applications, the minimum return loss must be 55dB.

Types Of The Fiber Optic Connectors For Fiber Optic Patch Cords

There are many types of fiber optic connectors. Here we introduce most of the types that are commonly used in fiber optic patch cord connectors on the market. According to the number of optical fibers used in a single connector, we can divide them into single fiber connectors and multifiber connectors, and according to whether their endfaces make contact when connecting, they can be divided into contact fiber optic connectors and non-contact fiber optic connectors.

Single fiber connectors are designed to use one fiber per connector, they can also be used for multi-core breakout or distribution fiber optic cables, and each branch fiber uses a single fiber connector. Most of the connectors are single fiber connectors, such as SC, ST, FC, LC, E-2000, MU, etc. Of course, for SC, LC, we often see duplex connectors, they use clips to combine two single fiber connectors together, the clips can easily be removed to separate the two combined connectors. Common multifiber connectors are MT-RJ, MPO, MTP these types. One connector of MT-RJ has two fibers, MPO connector pack 4core to 72core fibers in a single ferrule in one connector.

Most of the fiber optic connectors are contact connectors, and the end faces of non-contact connectors do not have physical contact when mated. Typical is the SMA connector, which is an ancient connector, and its invention even predates the appearance of single-mode fiber.

LC (Lucent connector) is one of the most common and popular connectors at present. The name of LC comes from Lucent technologies. LC uses 1.25mm ferrule. The size of the entire connector is only half of SC, so it is also called MINI-SC. LC represents the development direction of optical communication connector – miniaturized, low cost, suitable for dense installation. LCs are widely used in optical communication equipment in data centers.

SC (Subscriber connector) comes from Nippon Telephone and Telegraph (NTT), SC uses 2.5mm ferrule and a snap-in connection. SC is a very common optical fiber connector, and SC connector is used in most scenarios in FTTH applications.

ST (straight tip) connector is developed by AT&T, it is metal structure and must be twisted to lock into use. ST has gradually faded out of the market, but still used in some places.

FC (face contact) connector is a rugged metal connector with a screw-on connector cap and 2.5mm ceramic ferrule. The screw-on structure of FC contributes to the firm and reliable optical fiber connection, and it is still the interface of many optical communication devices, such as using on some fiber video converters.

E2000 fiber optic connector adopts the push-pull locking setting, which is easy to install. The shell is made of engineering plastics, which is convenient for intensive installation. It is mainly used for single-mode optical fiber, and the connector comes with a dust cover and ceramic ferrule.

MU (Miniature unit coupling) connector is one of the world’s smallest single-core optical fiber connector developed by NTT based on the SC-type connector that is currently the most used. The connector uses a 1.25mm diameter sleeve and a self-retaining mechanism, which has the advantage of high-density mounting.

MPO/MTP: Mainly used in data centers, supporting 40G (12 cores) and 100G (24 cores) fiber channels. MPO/MTP connectors are divided into two types: connectors with guide pins (male) and connectors without guide pins (female). MTP connectors are an upgraded version of MPO connectors, with better transmission performance and lower loss.

MDC: (Mini-DuplexConnector) The MDC connector is developed by USCONEC. Compared with the previous connector, it is smaller than the previous connector. It belongs to 4 channels and supports 8 cores. It is used in high -density data centers to connect. It has created a new era of dual fiber connection. The polarity of the MDC connector can be easily changed on the spot or the factory to support multiple wiring methods without having to use tools, no exposure or distorted fiber. MDC is a dual -fiber connector, which uses an industrial standard LC connector 1.25mm metal technology. The MDC adapter of the three -terminal port is directly installed in the standard panel opening of the dual LC adapter, which increases the density of fiber.

CS: The CS connector is an ultra -compact dual -core connector designed by Senko. As shown in the figure below, compared with the dual -work LC, its size is reduced by 40%, which saves space. Design makes the cable more compact; CS can also be equipped with 48mm push lever, which is more convenient to operate in high -density applications. The CS connector is designed for 200G/400G QSFP-DD and OSFP applications. Increasing the density and capacity of 400GB of optical fiber ports, it is an ideal choice to meet the needs of ultra-high-density light in the application of ultra-large-scale data centers and edge computing applications.

SN: SN is a new type of connector launched by Senko after CS. The SN connector belongs to the next -generation high -density connector, dual -connected connector, which is optimized for 400G and next -generation data centers. Compared with LC dual fiber, the SN size effectively reduced. It also uses the 1.25mm metal mature LC duplex technology.

The CS, SN and MDC belong to the so called VSFF (Very small form factor) connectors.

Above connectors are still popular to use today, below connectors are old styles and are fading or already faded in the market.

MT-RJ:

MT-RJ connector is designed to emulate the RJ-45 modular plug in fit and ease of use. MT-RJ features two fibers in one single ferrule. MT-RJ also have female type and male type connectors. However, both are legacy connectors now.

VF45: made by 3M company in the 1990s, VF45 is not popular these days.

LX5: this connector looks like E-2000 and LC. It is also a small form connector for CATV, LX.5 is already end of life but manufacturers like Sunrise Photonics still have them available.

D4: D4 is an old-style fiber connector with 2.5mm ferrule and a threaded connector cap. It is similar function to FC fiber connector, but its shape is smaller than the FC. D4 is seldom used today.

Mini-BNC: (Bayonet Nut Connector) is a metal twist-lock connector with 2.5mm ferrule. Mini-BNC is old style legacy connector.

FDDI: (Fiber Distribution Data Interface), it is a big size plastic body duplex connector. It is used to link electronics and fiber transmission equipment. FDDI is seldom used today, and its components are not available.

ESCON: (Enterprise System Connection) is from IBM in the early 1990s. it looks like FDDI and is also big size.

SMA: (SubMiniature A), this connector is from Amphenol and is very old, it was originally developed even before the invention of single mode optical fiber. It cannot provide precise connection as more recent connectors. SMA can still be found in military equipment.

Biconic: The Biconic connector has a cone-shaped ferrule. These connectors do not have an alignment key that can rotate during the mating process; they are non-contact connectors like SMA connectors (non-contact). Biconic is considered a legacy connector, but they are still used in military cabling. For some TFOCA cables, the Biconic connector ferrules are incorporated inside.

Color Code Of The Fiber Optic Connectors

ANSI/TIA-568-C.3 section 5.2.3 specifies the color code standard for fiber optic connector. By adopting such an industry standard, we can easily tell from the color of the connectors which fiber they are used for.

Geometry: (PC, UPC, APC, Flat and Lensed ferrules)

In fiber optic communications and connector/patch cord field, geometry refers to the shape of the ferrule endface. There are 4 types of geometry shapes: flat, curved (PC and UPC polished), Angled (APC polished) and lensed.

Flat endface

Flat endface seems the best at first sight, but it is not true. There are always some polishing irregularities when making flat endface, this cause problems and the optical loss is never as good as expected. Due to the disadvantages of flat endface, manufacturers do not use it in fiber connectors/ patch cords ferrule polishing.

Curved

The best geometry for physical contact (PC) of the connector ferrule is curved, PC polished ferrule ensure the apex (highest feature) is the center of the optical fiber end. At first manufacturers use PC polish but later UPC (Ultra PC) is developed to replace the old PC style. The end face of the UPC connector is not completely flat but as PC it also has a slight curvature for more precise mating. UPC is based on PC with more optimized end surface polishing and surface finish, and the end surface looks more dome shaped. Now PC is already abandoned and replaced by UPC.

Angled

Angled polish ferrules are intended to reduce the return reflection. This is called angled PC (APC) polish, it has an angle of 8 degree on the end face of ferrule. By using this design, the ferrule and fiber end is angled, light that is reflected will be sent to the cladding of the optical fiber and absorbed by the coating. It will not go back via the fiber core to the transmitting end. In this way we can avoid the back reflection (return reflection) interfering the operation of the transmitter.

Lensed

Lensed ferrule is not a recent invention, it actually existed decades ago. Only recently has it become known as expanded beam.

There are two types of Lensed ferrule, imaging lens and collimating lens, most of the expanded beam connectors are made of collimating lens. The advantage of expanded beam connectors over physical contact fiber connectors is that,

• Better coping with particle contamination
• easier to clean
• Signal transmission without physical contact
• More effective protection of fiber core
• No need for great mating forces

Expanded beam connectors with lensed ferrules are usually used in military, avionics, aerospace and mining applications. they usually come with heavy duty connectors and cables for harsh environment.

Interferometer and three-dimension (3D) test

The Interferometer is a device specially used to test the endface of the optical fiber connector. It will generate a three-dimension (3D) map of the test results. We can see the status of the connector ferrule endface very intuitively through the image. Its test report contains the following contents: radius of curvature, fiber height (undercut or protrusion), apex offset, fiber diameter, ferrule angle, key angle and epoxy width. The first three items of these parameters are the most critical data. Required by Telcordia GR-326, a quality measurement standard for single-mode fiber optic connectors and single-mode fiber patch cords.

Radius of curvature

Radius of curvature means the roundness of the fiber connector ferrule endface. It is measured from the center axis of the ferrule. Telcordia GR-326 define this value should be within the range of 7mm to 22mm. values outside this range is not acceptable.

Apex offset

Apex offset of the fiber optic connector endface is the highest place of it. The apex should be exactly in the center of the optical fiber, this is the ideal situation. In actual operation, it has an allowable tolerance range. Telcordia GR-326 define the apex offset should not exceed 50um.

Fiber Height (undercut or protrusion)

Fiber height means the optical fiber’s position below or above the rounded ferrule end face. If it is too far above the endface, it is easily got damaged when mating with another ferrule/connector. If it is too far below the endface, there is air gap which will result in higher loss. Telcordia GR-326 define the value range acceptable is +-55nm.

The quality of patch cords and cables is first place, but so is their installation. Improper installation can cause fiber patch cords to be damaged or not work properly.

Some fiber optic patch cords are customized, and their installation needs to be according to the manufacturer’s specifications, but most fiber optic patch cords and cables have common characteristics, and they can comply with common installation specifications. The optical communications industry has two standards to regulate the installation of fiber optic cables and fiber optic patch cords: ANSI/TIA-568-C.0 and ANSI/TIA-568-C.3. Four general types of fiber optic patch cord/cables are defined in section 5.4.1 of ANSI/TIA-568.C-0. Of all the parameters for the installation of fiber optic cables and fiber optic patch cords, the two most important are bend radius and tension strength( pull strength).

• Inside plant cables: fiber optic patch cords designed for building interior.
• Indoor/outdoor cables: They are not outdoor cables, they are fiber cables/patch cords typically used to connect between buildings.
• Outside plant cables: they are backbone cables, heavy duty.
• Drop cables: drop cables and patch cords link between the drop terminal and the premise terminal. Typical types of such cables are FTTH drop cables.

Please note although ANSI/TIA-568-C.0 and ANSI/TIA-568-C.3 provides the standards, not all cables comply with all the standards. You should always check the manufacturer’s data sheet for the optical cables/ patch cords you use for the cable bend radius and tension strength/pull strength parameters.

Use pulling eyes to help with fiber optic patch cords installation

Pulling eye is an essential tool when you need to pass fiber patch cords through pipes or walls or some other areas that are difficult to reach by manpower. The Pulling eye (pulling grips) of Sunrise Photonics has two functions. The first is that it has a sheath surrounding one end of the fiber optic patch cord, and all connectors and branch structures are wrapped in it for protection. The second is that its pulling line is directly connected to the strength member of the fiber optic jumper or cable, so that the fiber optic jumper will not be damaged when pulled. Pulling eyes are very effective tools when you need pull cable through the conduit, if necessary, you can also choose to add pulling eyes on both side of the optical fiber patch cords.

Standard Of Fiber Optic Patch Cord

The recognized industry standard for fiber optic patch cords is ANSI/TIA-568-C.3, which specifies the performance that fiber optic patch cords should achieve in premise cabling. ANSI/TIA-568-C.3 section 4.2 and 4.3.1 regulations are the physical standards of optical fiber jumper and its optical transmission. Section 5.2 of ANSI/TIA-568-C.3 specifies standards for fiber optic connectors and adapters. Section 6.4 of ANSI/TIA-568-C.3 specifies the structure types of optical fiber jumpers, including simplex, duplex, and array types. Simplex cable contains only one core, duplex contains two cores, and array cable is a kind of multifiber cable, but different from fanout cable, distribution cable or breakout cable, it has only one ferrule, in this one ferrule, optical fibers are arranged in a row or rows and columns. The typical array cable is MPO and MTP.

ANSI/TIA-526-14 Optical Power Measurement Method

ANSI/TIA-526-14 describes three methods for testing cable plants. The difference between them is the number of test jumpers used. The reference power measurements they get are also different. Method A uses two test jumpers, can test the loss of the cable plant plus one connection loss. Method B uses one test jumper, can test the loss of the cable plant plus two connection loss. Method C uses three test jumpers, it Only the loss of the cable plant can be tested. Here we show how to use Method A to test patch cord power loss measurement and connector insertion loss measurement.

Fiber Optic Patch Cord Power Loss Measurement

The loss power measurement test of multimode fiber patch cords can use the method described in ANSI/TIA-526-14. Here the fiber optic patch cord is substituted for the cable plant described in Method A test. Because the length of the fiber jumper is usually only 3 meters and 5 meters, its optical loss can be ignored. We usually test at 850nm or 1300nm. By using this test, you can get the loss of the patch cord connector pair. ANSI/TIA-568-C.3 specifies a maximum loss of 0.75dB for the patch cord connector pair. Sunrise Photonics’ fiber patch cord production standard is higher than ANSI/TIA-568-C.3.

After we have prepared the optical fiber test equipment and patch cords according to the test procedure described in ANSI/TIA-526-14, we clean the connectors of the optical fiber patch cord, make sure the test fiber patch cord’s optical fiber and connectors exactly match with the patch cord you are going to test, meanwhile ensure both test patch cord and the tested patch cord are without sharp bends.

Test patch cord and tested patch cord connectors are easily accessible, so optical power loss should be measured in both directions, taking the average of the two tests as the loss of the fiber optic patch cord. If the average value exceeds 0.75dB, then it is not a qualified fiber patch cord.

Connector Insertion Loss Measurement

We can also use Method B to test fiber loss for a single connector. The first step is to connect the test jumper directly between the power meter and the light source. Then write down the value displayed by the power meter, which is the reference power measurement. In the second step, we disconnect the test jumper from the power meter but keep the connection with the light source unchanged. In the third step, we connect the tested patch cord between the test jumper and the power meter to form a complete test chain, and then we record the displayed value of the power meter, which is the test power measurement. Then the loss of the single connector tested It is the difference between test power measurement and reference power measurement. If the former value is -20.6dBm and the latter is -20.8dBm, then the insertion loss of the connector is the difference of 0.2dB, which is within the range specified by the industry standard.

As we have known before, all kinds of optical fibers have a basic structure. The same is true for fiber optic cables. A fiber optic cable may contain one optical fiber or multiple optical fibers, and it may be composed of different materials and used in different occasions. But these cables also have a common basic structure, they all include optical fiber (consists of core, cladding, and coating), a buffer, a strengthened member, and outer protective jacket (or named sheath). Below we discuss these parts separately.

Buffer

Coating is the first protective layer of the optical fiber core, which is tightly surrounded by the cladding, and the buffer is the second protective layer of the optical fiber, which surrounds the coating. There are two types of buffers, one is loose buffer, and the other is tight buffer.

Loose buffer

Loose buffer is also called loose buffer tube or loose tube buffer. The inner diameter of the buffer layer/tube of the loose buffer is much larger than the diameter of the fiber core, so the coated optical fiber can easily move in the buffer tube, which is why it is called loose buffer fiber optic cable.

One of the main reasons for using loose buffer is that this structure can be applied to the reason that the operating temperature will change greatly, because there are other materials in the optical cable besides the optical fiber, and their ratio of expansion or contraction with temperature is different, loose buffer That leaves plenty of room for them to change with temperature. Another advantage of the loose buffer is that if we need to pull or move the fiber out of the tube, we don’t need to put too much force on the fiber, thus avoiding damage to the fiber and cable.

Loose buffer fiber optic cable may be a single-core structure or a multi-core structure. In a multi-core fiber optic cable, there is usually a central core without optical fibers, and all loose buffer tubes surround this central core. The central core increases the cable’s resistance to bending and tensile force.

Loose buffered fiber optic cables are usually used for both indoor and outdoor use. When used outdoors, the tube is often filled with gel for waterproof and moisture-proof. They are also used for outdoor aerial cables and direct buried cables.

Tight buffered cable

tight buffered fiber optic cables are typically used indoors. Usually, the coating of indoor optical cable is 250um, and its buffer is 900um. The diameter of tight buffer fiber cable is smaller than that of loose buffer, and its minimum bend radius is also smaller. These characteristics make tight buffer cables more suitable for indoor and some need tight bends.

Normally the fiber optic patch cords use tight buffered structure by default.

Strength members

The main function of strength members is to increase the tension strength and prevent damage to the optical cable when it is subjected to tension. Strength members may be located in the center of the optical cable structure or may be located outside the buffer and inside the outer skin. There may be more than one strength member in a fiber optic cable, depending on the purpose of the fiber optic cable and the design structure of the fiber optic cable. The most common strength member materials include aramid yarns, fiberglass rods and stainless steel.

Aramid yarns, usually Kevlar, are a light, flexible and strong material that is also used to make sails, body armor and firefighting gear. The Kevlar in the optical cable increases the bending resistance and tensile strength of the optical cable. It is a very common strength member in the optical cable, and you will see it in almost every optical cable.

Large fiber optic cables, especially for outdoor optical cables, usually use fiberglass or steel as the strength member, stainless steel can effectively protect the optical cable from being damaged by excessive bending and installation tension. But steel is not suitable for all occasions, for example, sometimes we need a dielectric fiber optic cable (ADSS fiber cable), then steel is no longer applicable.

Fiber Optic Cables Jacket

Jacket is the outermost protective layer. Different optical cables are used for different occasions and purposes. Considering factors such as sunlight, ice and snow, temperature, chemicals, rodent damage, etc., the outer sheath of the optical cable is made of different materials. There are four main cable sheath materials:

Polyvinyl Chloride (PVC), PVC is commonly used in indoor optical cables, it has certain fire resistance and is soft and flexible. PVC is waterproof but cannot withstand solvents, and PVC is not suitable for working at low temperatures.

Polyethylene (PE), PE is a common outer sheath material for outdoor optical cables, it is suitable for various operating temperatures and waterproof. Formulated PE has the properties of Low smoke zero halogen.

Polyvinyl difluoride (PVDF), the main properties of PVDF are LSZH and fire resistance, it is a typical sheath material of plenum rated fiber optic cable. PVDF is not as soft and flexible as other types of skins, and its fire resistance is its main role.

Poly tetra fluoroethylene (PTFE), this sheath material is mainly suitable for aerospace fiber optic cables. It has low coefficient of friction and can be used in extreme temperature up to 260 degrees Celsius.

Core

The core is the most important part of the optical cable, and light is transmitted through the core. We often see all kinds of fiber optic cables and fiber optic patch cords, no matter what color they are, what kind of material they are, what kind of structure they are, they all have extremely thin fibers inside as their main part. The other parts are composed around the fiber core. Communication optical fibers are usually made of glass, that is pure silicon dioxide (SiO2). Its chemical composition is consistent with the main composition of natural sand, but the fiberglass used for optical communication must be very, very pure.

Fiber cores have different diameters to meet different applications. There are three commonly used sizes: 9um, 50um and 62.5um. 9um is used for single mode fiber, 50um and 62.5um are used for multimode fiber, 9um single mode fiber is OS1 or OS2, 62.5um multimode fiber is OM1, 50um is used for Multimode OM2, OM3, OM4 and OM5. The diameter of a typical fiber core is between 3.7um and 200um, the diameter of plastic fiber is generally much larger than that of glass fiber, and the typical diameter of plastic fiber is 980um.

Cladding

The optical fiber cladding is one of the three major components (core, cladding, coating) of the optical fiber. The core and the cladding constitute the most basic optical fiber structure. The transmission principle of the optical fiber is to form total reflection between the core and the cladding.

The core is in the innermost layer, and the cladding is tightly surrounded by the core, providing a lower refractive index to make the fiber light transmission workable. The cladding and the core are made of the same material (SiO2). The cladding and core were made at the same time and fused together. During the fabrication of the fiber, different numbers of dopants were added to the core and cladding to maintain the difference in their refractive indexes (about 1 percentage point more difference).

At 1300 wavelength, the typical refractive index of fiber core is about 1.49, and the refractive index of cladding is about 1.47. These numbers are not fixed, and the refractive index of the same fiber core will be different under different working wavelengths. For example, at 850nm, the refractive index of the fiber core will increase slightly.

Like fiber core, cladding also has standard sizes, the most commonly used are 125um and 140um, of which 125um can support 9um, 50um and 62.5um fiber core. This is what we often call 9/125 single mode fiber, 50/125 multimode fiber and 62.5/125 multimode fiber.

Coating

Coating is located in the outer layer of core and cladding. Its only function is to protect core and cladding. Although it does not participate in the transmission of signals, it is crucial and indispensable. Without its protection, the fiber structure would be very fragile and easily damaged. Usually, the diameter of the coating is 250um or 500um, and sometimes the coating is colored, which can help people identify the different strands of the optical fibers in multi-core optical fibers.

There are different types of materials for coating, and the material used depends on the actual application scenario of the optical fiber. The most common coating is made of acrylate. This coating consists of two layers, the inner layer is relatively soft, and its main function is to protect the optical fiber from being broken when it is bent. The outer second layer is relatively hard and is used to protect the inner first layer of coating. The working environment temperature of Acrylate should not be too high. About 100 degrees Celsius is the limit for Acrylate

Acrylate is not suitable for harsh environments such as oil, mining, aerospace, and people have invented coatings made of silicon, carbon and polyimide. We will briefly describe these three materials separately.

The advantage of Silicone is that it can work at high temperature, its working environment temperature can be as high as 200 degrees Celsius, silicone is moisture-proof and not easy to burn. It can effectively protect the fiber when the fiber is bent. But the disadvantage of silicone is also obvious, it is not hard enough, so it must be used with other protective materials.

Carbon coating is the thinnest of all materials, usually only a micron thick. Carbon coating perfectly seals the inner glass fiber, protecting it from moisture and increasing the working life of the fiber. Carbon also cannot be used alone as the only coating material; it must also be used with other materials like silicone or polyimide.

Polyimide is an optical fiber coating material widely used in the aviation field; it can work normally at a high temperature of 350 degrees Celsius. Its coating thickness is about 15um, which is thinner than acrylate or silicone coating, but thicker than carbon coating.

Standards for optical fiber and optical fiber cables

Optical fiber is a tiny and delicate product. The construction of optical fiber network must be precise. A small flaw such as misalignment of the fiber core may cause the entire network to fail to work. Therefore, industry standards are necessary for optical communications.

There are many different organizations and agencies that publish their industry standards. Well known such organizations are TIA (telecommunications industry association), ITU (international telecommunication union), ISO (International Organization for Standardization) and IEC (international electrotechnical commission). Among all these published standards, we are more familiar with the ITU and IEC standards for single-mode and multi-mode fibers.

• ITU-T G.651.1, characteristics for 50/125 multimode graded index optical fiber and optical cable.
• ITU-T G.652, characteristics for single mode fiber and cable. Typical fiber is G652d as we normally use them to assemble fiber patch cords.
• ITU-T G.655, characteristics for non-zero dispersion-shifted single mode fiber and cable.
• ITU-T G.657. characteristics for bend insensitive single mode fiber and cable.
• IEC 607932-2-10, Category A1 multimode fiber optic products.
• IEC 607932-2-50, Class B single mode fiber optic products.

The above standards specify the performance of optical fibers, optical cables and optical fiber assemblies, they are general standards in the optical communication industry.

The ANSI/TIA-568-C standards and the ISO/IEC 11801 standard are applicable to premises cabling components; premises cabling includes both copper and fiber-optic cabling.

Tension Strength of the optical fibers

Tension strength is one of the characteristics of optical fibers that needs our special attention. Tension strength is important because this property affects how fiber optic cables are installed, bend curvature, and work performance. Tension strength means the maximum tensile force that the fiber can withstand. When the tensile force exceeds this value, the fiber will be broken. The fiber optic cables we usually make and use take this factor into account, and they all have relatively high tension strength tolerance.

The tension strength of optical fiber is mainly borne by cladding, and the unit of measurement of tension strength is kpsi (thousands of pounds per square inch). The maximum tensile force that the fiber can withstand is 1.9 pounds. In general, we recommend that the maximum tensile force applied to the fiber does not exceed 0.5 pounds when removing buffer or coating in actual work.

Note that when the outer sheath of the optical cable is damaged or scratched, the tension strength there will be gone.

Minimum bend radius

Minimum bend radius is the maximum bend that the fiber can withstand without the fiber being damaged.

Since the fiber is stress sensitive, bending the fiber can cause the optical signal to escape through the fiber cladding, and as the bend becomes sharper, the optical signal will leak more. Bending can also cause microcracks that can permanently damage the fiber. Adding to the trouble is that microbend points are difficult to find and require expensive test equipment, at least the jumpers must be cleaned or replaced. Fiber bending can cause fiber attenuation. The amount of attenuation due to fiber bending increases as the bend radius decreases. The attenuation due to bending is greater at 1550 nm than at 1310 nm, and even greater at 1625 nm. Therefore, when installing fiber jumpers, especially in high-density wiring environments, the jumper should not be bent beyond its acceptable bending radius.

The ANSI/TIA/EIA-568B.3 standard defines minimum bend radius standards and maximum tensile forces for 50/125 micron and 62.5/125-micron fiber optic cables. The minimum bending radius will depend on the specific optical fiber cable. In the case of no tension, the bending radius of the optical cable should generally not be less than ten times the outer diameter (OD) of the optical cable. Under the tensile load, the bending radius of the optical cable is the outer diameter of the optical cable. 15 times. Industry standards for traditional single-mode patch cables typically specify a minimum bend radius of ten times the outer diameter of the jacketed cable or 1.5 inches (38mm), whichever is greater. The commonly used G652 fiber has a minimum bending radius of 30mm.

G657 has a smaller bending radius, including G657A1, G657A2, G657B3, the minimum bending radius of G657A1 is 10mm, G657A2 fiber is 7.5mm, G657B3 fiber is 5mm. This type of fiber is based on the G652D fiber, which improves the bending attenuation characteristics and the geometric characteristics of the fiber, thereby improving the connection characteristics of the fiber, also known as the bending attenuation insensitive fiber. Mainly used in FTTx, FTTH, suitable for use in small indoor spaces or corners.

Both fiber breaks and increased attenuation can have a significant impact on long-term network reliability, network operating costs, and the ability to maintain and grow a customer base. Therefore, we need to clearly know the minimum fiber bend radius in order to keep the cable or patch cord in good working condition.

Mode

When light travels in the fiber core, it can take different and many possible paths. As a complex electromagnetic wave, light waves are much smaller than the core of a fiber. The transmission path of light depends on several factors, including the size of the fiber core, the wavelength of the light source, and the numerical aperture. The transmission path of light, or its mode, is also an important feature to distinguish optical fibers.

When the core is very small and can only allow one mode, we call it single mode, and when the core is large enough to allow light to transmit through the core using different modes/paths, we call it multimode.

Numerical Aperture and modes

The value of Numerical Aperture can be calculated using the following formula:

NA =

We already know that Mode is related to Numerical Aperture, and the relationship between them can be expressed by the following equation:

Mode = (D x x NA /)² /2

Let’s take an example to illustrate that when the core’s refractive index value is 1.485 and the cladding’s value is 1.47, and we assume that the core’s diameter is 50um, we can calculate from the above two equations,

NA= 0.211

Mode = 760.2

Because the value of mode must be an integer, we take the integer 760.

Refractive Index Profiles

Depending on the fiber structure and the wavelength of the light source, the fiber may support from a single mode to as many as one million. Light may travel in straight lines through the core, or it may travel with constant reflections at acute or obtuse angles.

The schematic diagram of the refractive index profile intuitively shows the relationship of the refractive index between core and cladding. There are four common refractive indexes in the field of optical fiber communication: step index, graded index, depressed clad step index and depressed clad graded index.

Multimode step index fiber

Multimode step index fiber is completely unsuitable for telecommunications, and the industry standards for the optical communications industry that we mentioned in this article are also unsuitable for this fiber. Because in this fiber, its modal dispersion offsets light rays by about 15ns/km to 30ns/km, it is assumed that one beam of light takes the shortest path through this fiber, and the other beam takes the longest path through this fiber, they produce a 15 to 30 nanoseconds difference in arrival time at a distance of 1Km. This means that every bit must be separated by at least 30ns in every kilometer distance, otherwise the signals may overlap, which makes it far from meeting the requirements of processors, transmitters, and receivers in the telecommunications field. Therefore, Multimode step index fiber is mostly suitable for the field of plastic optical fiber.

In order to reduce modal dispersion, people developed multimode graded index fiber and single mode step index fiber.

Multimode Graded index fiber

Multimode graded index fibers solve the problem of modal dispersion by increasing the speed of high order ray so that they can keep up with the speed of low order ray. Graded index fibers consist of many concentric glass layers with refractive indexes that decrease with the distance from the center.

With this improved graded index fiber, beams that travel farther in the fiber due to different angles of incidence can now travel from one end of the fiber to the other end of the fiber at a very similar time to the direct beam. Modal dispersion in graded index fiber can be reduced to as low as 1ns/km level. This makes it perfect for telecom fiber applications.

Single mode step index fiber

Single mode step index fiber adopts another idea to reduce modal dispersion. The core of this kind of optical fiber is so small that it can only allow light to be transmitted in one mode. The core of single mode step index fiber is only 8um to 10um.

We should pay attention to a situation where the wavelength will also affect the mode of fibers. Let’s take fiber for 1310nm single mode as example, if it uses 850nm wavelength for transmission, it will have more than one possible mode. We have a term cut wavelength to denote the minimum wavelength at which an optical fiber transmits in a single mode. In a typical 1310nm single-mode fiber, its cutoff wavelength is about 1260nm

Depressed Clad fiber

Both single-mode and multimode optical fibers have the types of suppressed clad, which are often called bend insensitive fiber. In the FTTH field, optical cables often encounter use scenarios with great bending. Bending causes light loss and affects signal quality.

Optical fiber manufacturers have created bend insensitive fibers to reduce the attenuation of optical fibers when they are bent. The method they use is to use an optical trench in the optical fiber. The optical trench tightly surrounds the core of the fiber. It has lower refractive index than core and cladding. This low refractive index acts as an obstacle to light escaping from the fiber core when the fiber is bent, thereby reducing light attenuation. Usually, the size, position and exact refractive index value of the optical trench are proprietary, and the data is not public.