Which Fiber Loopback Should I Use for My Transceiver?

In telecommunication, fiber loopback is a hardware designed to provide a media of return patch for a fiber optic signal, which is typically used for fiber optic testing or network restorations. When we need to know whether our fiber optic transceiver is working perfectly, we can use a fiber loopback cable as an economic way to check and ensure it. Basically, the loopback aids in debugging the physical connection problem of the transceiver by directly routing the laser signal from the transmitter port back to the receiver port. Since fiber optic transceivers have different interface types and connect different types of cables, it is not that simple to choose a right loopback for our transceiver. This post will be a guide on how to choose a right loopback cable for specific transceiver module.

Fiber Loopback Types and Configurations

Before deciding which loopback cable to use, we should firstly know the structure and classification of fiber loopback cable. Generally, a fiber loopback is a simplex fiber optic cable terminated with two connectors on each end, forming a loop. Some vendors provide improved structure with a black enclosure to protect the optical cable. This designing is more compact in size and stronger in use. Based on the fiber type used, there is single-mode loopback and multimode loopback, available for different polishing types. According to the optical connector type of the loopback, fiber loopback cables can be divided to LC, SC, FC, ST, MTP/MPO, E2000, etc. In testing fiber optic transceiver modules, the most commonly used are LC, SC and MTP/MPO loopback cables.

lc&sc loopback cable
Figure 1: LC & SC Loopback Cable

The LC and SC loopbacks are made with simplex fiber cable and common connectors; it’s not difficult to understand their configurations. As for the MTP/MPO loopback, it is mainly used for testing parallel optics, such as 40G and 100G transceivers. Its configuration varies since the fiber count is not always the same in different applications.

8 Fibers MTP/MPO Loopback Cable Configuration

In a 8 fibers MTP/MPO loopback, eight fibers are aligned on two sides of the connector, leaving the central four channels empty. And the fibers adopt a straight configuration of 1-12, 2-11, 5-8, 6-7. The polarity channel alignment is illustrated in the following figure.

8 Fibers Loopback Polarity Channel Alignment
Figure 2: 8 Fibers Loopback Polarity Channel Alignment
12 Fibers MTP/MPO Loopback Cable Configuration

The only difference between the 12-fiber MTP loopback and the 8-fiber loopback is that the central four channels are not empty. Its alignment is 1-12, 2-11, 3-10, 4-9, 5-8, 6-7.

12 Fibers Loopback Polarity Channel Alignment
Figure 3: 12 Fibers Loopback Polarity Channel Alignment
24 Fibers MTP/MPO Loopback Cable Configuration

The 24 fibers MTP loopback also adopts type 1 polarity. Its alignment design is shown below.

24 Fibers Loopback Polarity Channel Alignment
Figure 4: 24 Fibers Loopback Polarity Channel Alignment
Which to Choose for a Specific Transceiver?

Considering the common features of the transceiver and the loopback, we should think about the connector type, polish type, and cable type when selecting a loopback for the transceiver. The selection guide for some mostly used transceiver modules is summarized in the following tables.

Table 1: Loopback choices for 10G SFP+ transceivers

Model Interface type Cable Type Suited Loopback
10GBASE-USR LC Duplex (PC) MMF

LC/UPC Duplex Multimode Fiber Loopback

10GBASE-SR LC Duplex (UPC) MMF
10GBASE-LR LC Duplex (UPC) MMF
10GBASE-ER LC Duplex (UPC) SMF

LC/UPC Duplex Single-mode Fiber Loopback

10GBASE-ZR LC Duplex (PC) SMF

Table 2: Loopback choices for 40G QSFP+ transceivers

Model Interface type Cable Type Suited Loopback
40GBASE-CSR4 MTP/MPO (UPC) MMF

8/12 Fibers MTP/UPC Multimode Fiber Loopback

40GBASE-SR4 MTP/MPO (UPC) MMF
40GBASE-PLRL4 MTP/MPO (APC) SMF

8/12 Fibers MTP/APC Single-mode Fiber Loopback

40GBASE-PLR4 MTP/MPO (APC) SMF
40GBASE-LR4 LC Duplex (PC) SMF

LC/UPC Duplex Single-mode Fiber Loopback

40GBASE-LR4L LC Duplex (UPC) SMF
40GBASE-ER4 LC Duplex (UPC) SMF
40GBASE-LX4 LC Duplex (UPC) MMF/SMF

LC/UPC Duplex Multimode/Single-mode Fiber Loopback

Table 3: Loopback choices for 100G QSFP28 transceivers

Model Interface type Cable Type Suited Loopback
100GBASE-SR4 MTP/MPO (UPC) MMF

8/12 Fibers MTP/UPC Multimode Fiber Loopback

100GBASE-PSM4 MTP/MPO (APC) SMF

8/12 Fibers MTP/APC Single-mode Fiber Loopback

100GBASE-LR4 LC Duplex (UPC) SMF

LC/UPC Duplex Single-mode Fiber Loopback

Table 4: Loopback choices for CFP transceivers

Model Interface type Cable Type Suited Loopback
40GBASE-SR4 CFP MPO/MTP (UPC) MMF

8/12 Fibers MTP/UPC Multimode Fiber Loopback

40GBASE-LR4 CFP SC Duplex (UPC) SMF

SC/UPC Duplex Single-mode Fiber Loopback

40GBASE-FR CFP SC Duplex (UPC) SMF
100GBASE-LR4 CFP SC Duplex(PC/UPC) SMF
100GBASE-ER4 CFP SC Duplex(PC/UPC) SMF
100GBASE-SR4 CFP MPO/MTP (UPC) MMF

24 Fibers MTP/UPC Multimode Fiber Loopback

Conclusion

This post discusses specific fiber loopback choices for some most commonly used fiber optic transceivers. For other transceiver modules that are not mentioned in this post, we can also know how to choose a suitable loopback for it by getting details about its interface type, physical contact and cable type.

Importance of Using Fiber Color Codes in Data Center

The utilization of fiber color code in data center effectively helps technicians make better cable management and reduce human errors. Without redundant checking process, people can easily get the information of the device by only one look. Making good use of the color code system can surely save much time during work. This article will mainly present the widely accepted color code system and its important functions.

fiber color code

Introduction to Fiber Color Code Systems

Fibers, tubes and ribbons in fiber optic cables are usually marked with different color codes to facilitate identification. There are many color code systems for national or international use. All these systems are characterized by using 12 different colors to identify fibers that are grouped together in a common bundle such as a tube, ribbon, yarn wrapped bundle or other types of bundle.

Different color code standards may be used in different regions. For example, the S12 standard is used for micro cables and nano cables in Sweden and other countries. The Type E standard is defined by Televerket and Ericsson used in Sweden. The FIN2012 standard is used in Finland, etc. However, there is one color code system widely recognized in the world, namely the TIA/EIA-598 standard.

Specifications of TIA/EIA-598 Color Codes

The following picture gives the fiber color coding of TIA/EIA-598 standard. If more than 12 fibers or tubes are to be separated, the color sequence is normally repeated with ring marks or lines on the colored fibers and tubes. As for the fiber cable jacket, orange, yellow, aqua and black color codes are used for their distinction.

color-code-system

Functions of Fiber Color Code in Data Center
Distinguishing Fiber Grades

As mentioned above, the outer jacket color codes are able to identify the fiber grades. OM1/OM2 cables often adopt the orange jacket, OM3/OM4 cables with aqua jacket, single-mode cables with yellow jacket and hybrid cables (indoor/outdoor cables and outside plant cables) with black jacket. One thing to note is that the mix of OM1 and OM2 or OM3 and OM4 cables may be troublesome. You should make sure not to mingle these cables with the same color code.

Identifying Fiber Patch Cords

Using fiber color code to label fiber patch cords can reduce the potential for human error. For instance, you may highlight mission-critical patch cords in red, and then teach all technicians that a red patch cord should only be moved with proper authorization or under supervision. Likewise, keeping the fiber connector color consistent with fiber grade color standards will make it simple for technicians to use the right connectors with the cables.

Separating Different Ports

The color-coded port icons can be helpful in identifying different network routings in accordance with internal needs. By tagging each patch panel port, you can simplify and streamline network management.

Differentiating Connector Boots

You can use fiber color code on connector boots to make routine maintenance and moves, adds and changes easier by helping technicians preserve correct parallel groupings for switch ports. If you change your connector color, you need to ensure that your fiber cable color represents the fiber grade to avoid confusion. You can also change the color of a connector boot to differentiate between different aspects of the network, making it easy for technicians to view the contrast within a panel.

Conclusion

Visual management is more intuitive for specialists to supervise the data center. Color code system has provided an ideal and easy way to solve the cabling problem. Inside the cables, the fiber buffers are also color-coded with standard colors to make connections and splices easier. Therefore, if you are still bothered by these issues of fiber patch cables, using the fiber color code system is a good way to go.

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Things You Need to Know About ADSS Fiber Cables

When it comes to OSP (outside plant) deployment, many types of fiber optic cables are used for different OSP applications. ADSS (all-dielectric self-supporting) cable is the type that is strong enough to support itself between structures without using conductive metal elements. It is often installed along aerial transmission lines to be a communication medium for electrical utility companies. Both single-mode and multimode fiber can be arranged in ADSS cables. And when using single-mode fibers, the cable can carry the maximum of 144 fibers. But do you know the basic structures of ADSS fiber cable? What are the advantages of using ADSS cable? And how can you prevent ADSS cable from damage? This article will give you all the answers.

ADSS cable

Structures of ADSS Cable

There are generally two kinds of structures for ADSS cable. One is called as central tube structure. From the following picture, the fiber of a certain length is placed in a PBT loose tube filled with water-blocking material. Then it is wrapped with aramid yarn according to the desired tensile strength and extruded with PE or AT sheath. This structure has a smaller diameter and lighter weight. But the fiber length is limited.

adss-central-tube-structure

The other type of structure is called as stranded structure. The following picture shows that the fiber loose tubes are surrounding around a central strength member (usually as FRP material). And the rest parts are similar to the central tube structure. This type is able to obtain a longer fiber length. Although the diameter and weight are relatively big, it is better to be deployed for large span applications.

adss-stranded-structure

Benefits of ADSS Cable

There are many advantages of using ADSS fiber cable. The overall weight and diameter of the cable are small which is a relief to the towers and poles. And its total transmission range is large enough to reach up to 1200 meters. Using the polyethylene sheath will also protect the cable from corrosive effect. ADSS cable’s non-metallic structure makes it possible to be anti-lightning. And the aramid yarn helps the cable to have good tensile performance and temperature performance under extreme weathers. The maximum lifespan of ADSS fiber cables can even reach up to thirty years.

Precautions for ADSS Cable Damage

  • Point 1, since many cables are running through mountainous areas, it is inevitable that the cables will be scratched or bent when come across trees or rocks. Especially for the cable sheath damage, it will greatly harm the service life of cable because the surface can be corroded once exposed to the dust and salty environment. Thus, the cable installation should be under careful examination and monitoring.
  • Point 2, due to the partial force during the line construction, common accidents like broken fiber and high loss point can be occurred. Lots of people think it is the problem of cable quality, but actually, it is because of the wrong construction process. Therefore, taking control of the constant tension at a uniform speed during installation is very important.
  • Point 3, another common damage is the broken fiber at strain towers. This is because of the wrong operation or partial force on fibers. During the construction, installers must pay attention to the proper angle and pulling direction of fibers to avoid such accidents.

Conclusion

ADSS cable is ideal for installation in distribution as well as transmission environments. It does not need support or messenger wire, a single pass is sufficient for installation which makes it a cost-effective and simple way of setting up fiber optic networks. With careful installation, this type of fiber optic cable can bring much convenience for the proper application.

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Types of outdoor fiber optic cable

Applications for Outside Plant Fiber Optic Cables

Inside plant refers to the cabling running inside a building. Similarly, outside plant is the cabling running outdoors. Outside plant cables are thicker because of more durable insulation jackets. As for fiber optic communication, there are many types of outside plant fiber optic cables. Some have extra protections to prevent corrosion and other elemental interference. Outside plant fiber optics are widely used in telephone networks, CATV, metropolitan networks, utilities and so on. If you want to choose the right outside plant fiber optic cable, its applicable environment is an important factor for consideration. This post will introduce some common outside plant fiber optic cables and typical outdoor application environments.

Several Types of Outside Plant Fiber Optic Cables

Outdoor Breakout Cable

Outdoor breakout cable is perfect for rugged applications and installations that require increased performance. It is usually made of several bundled simplex cables wrapped in a common cable jacket. The fungus, water and UV protections and temperature durability are beneficial to its outside applications. Its design of individual fiber reinforcement enables the quick termination to connectors and omits the use of patch panels or boxes. With much less termination work, outdoor breakout cable is more cost-effective when small fiber counts and short distances are required.

outside plant cable -breakout-outdoor-cable

Outdoor Loose Tube Cable

Outdoor loose tube cable has the gel-filled design protecting the cable from moisture environment. The gel within the loose-tube construction stops the penetration of water and keeps it away from the fiber. Also, it keeps water from freezing near the fiber at low temperatures which reduces the chance of stress fractures. Fibers are bundled inside a small plastic tube that can protect fibers from outside stresses. Outdoor loose tube cable is often used in conduits, strung overhead or buried directly into the ground.

outdoor-loose-tube-cable

Outdoor Ribbon Cable

Outdoor ribbon fiber optic cable has high fiber counts and small cable diameter. It contains the most fibers in the smallest cable. These fibers are laid out in rows as ribbons, and ribbons are laid on top of each other. Likewise, it also has gel-filled protection to block outside water. Ribbon cable makes installation much faster and easier since mass fusion splicers can join a ribbon at once.

outdoor-ribbon-cable

Outdoor Armored Cable

Outdoor armored cable is a direct buried type that prevents itself from animal bite. The metal armoring between two jackets effectively prohibits rodent penetration. Outdoor armored cable can be divided into light armored and heavy armored types. The former has the protective plastic jacket with the same durability and longevity of a stainless steel cable with a lighter weight. The latter is wrapped in a wire circle to be applied for underwater regions that near shores and shoals.

outdoor-armored-cable

Outside Cable Plant Applications

Outside cable plant deployment can be implemented in many environments. Above-ground, underground, buried and underwater are the typical applications.

Above-ground Cable Plant

Above-ground cable plant can be exposed to extreme temperatures, and to humidity that varies with the seasons and with daily temperature changes. Cables under such circumstances should be durable to adapt to extreme weathers and water penetration.

Underground Cable Plant

Underground cable plant usually applies cables in underground structures including the utility holes, controlled environmental vaults, ducts and so on. The condition in utility holes and ducts sometimes can be corrosive because of man-made chemicals. Cables with corrosion-proof materials are perfect for this environment.

Buried Cable Plant

Buried cable plant applies cables directly into the soil. Cables can also be exposed to the same corrosive environment as underground plant. But animal bite is an additional problem. Cables for this application should be very tough to endure both chemical corrosion and animal attack.

Underwater Cable Plant

Underwater cable plant are located beneath the surface of water. The water can range from relatively pure to brackish, or to badly contaminated with industrial effluent. Cables for underwater plant are extremely rugged, with fibers in the middle of the cable inside stainless steel tubes and the outside coated with many layers of steel strength members and conductors for powering repeaters.

Conclusion

Unlike indoor cables, outside plant fiber optic cables must be wrapped in different layers to withstand the severe installation conditions. Choosing the right kind of outdoor cable can save you a great deal for long-term maintenance. And your project application is an important aspect that will affect the selection of fiber optic cables.

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Have You Chosen the Right Cable Jackets?

Have you noticed that patch cables are all wrapped in various jackets? These cable jackets are important to serve as the protection for inner cable parts. Different kinds of jackets can influence the applications as well. Knowing the differences in cable jackets will help you make better decisions when choosing cables. Lots of materials can be made as cable jackets to cope with different situations. This article will mainly introduce some common types and analyze their distinctions.

cable-jacket

PVC

PVC (polyvinyl chloride) is a common jacket type widely used for general patch cables. The low cost and easy manufacture contribute to its popularity around the world. You can find PVC jackets almost everywhere when patch cables are used. PVC material is highly moisture-resistant so that can be perfectly applied to humid environment. But it also has some defects that will limit the service lifespan. For example, PVC material often becomes fragile under direct sunlight and its flexibility is restricted when greater bending is required.

LSZH

LSZH (low smoke zero halogen) is the material that gives off low toxic and corrosive gas under fire. It greatly ensures the high visibility and low respiratory damage when cables come across open fire or short circuit fault. LSZH cable jacket is typically applied to areas where smoke factor is considered to be the most important, such as aircraft, rail cars, ships, buildings and so on.

OFNP

OFNP (optical fiber nonconductive plenum) is specified by NFPA (National Fire Protection Association), which has no electrically conductive component inside optical cables. This type of cable jacket can effectively prevent fire and emit low smoke. OFNP cable is the highest fire rating fiber cable and has no replacement. Places including ducts, plenums, and other building airflow areas are suitable for installation.

PUR

PUR (polyurethane) cable jacket is the thermoplastic material that is usually used in harsh environment. It provides both mechanical resistance and chemical resistance. Thus, PUR cable can be installed for industrial applications where strong protective coating is demanded. Also, its flexibility makes itself a good material for retractile patch cables in continuously flexing applications. But it is more expensive than the common cable jackets.

PTFE

PTFE (polytetrafluoroethylene) sheath is a synthetic fluoropolymer material suitable for extreme environment. It is very durable under both high and low temperatures and can not be affected by most oils, fuels and fluids. This kind of cable jacket is widely used in military, aerospace, coaxial, and appliance wiring applications.

Rubber

Rubber jacket is a good option for portable power applications in outdoor or wet environment. It has better performance than plastic materials in flexibility, high temperature resistance and durability. Other applications like mining submersible pumps, control circuits, motor and associated machinery, construction equipment, etc. are also available.

Silicone

Silicone is the synthetic rubber with greater flexibility and stronger resistance against extreme temperatures and chemicals. Of course, it does not operate as high temperatures as PTFE. But with the extremely supple characteristic, silicone cable sheath is perfect for applications where lots of wire bending are required. And when it encounters fire, only a small amount of smoke will be produced which is also environmental-friendly.

Conclusion

After reading this article, you may get a general idea about the current cable jacket types and where they should be used. And certainly, if you want to find the most suitable jacket for your project, knowing this information is not far enough. But I hope this article can let you understand the importance of choosing a right cable jacket in your future applications.

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