Introduction to LC Uniboot Fiber Patch Cables

In the past years, to meet the growing bandwidth needs, data center technologies and cabling structures have changed a lot. High density apparently becomes the trend. Data center has to install more and more fiber optic jumper cables in a given space, which makes cable management a more and more difficult problem. New products and technologies are applied to achieve high density in data centers. To find an easy-to-manage and space-saving method for high density cabling becomes an urgent issue for data center managers. In this post, a favorable high density fiber cabling solution—LC uniboot fiber patch cable, which is born to solve problems during high density cabling, will be introduced.

LC Uniboot Fiber Patch Cable vs Standard LC Fiber Patch Cable

LC fiber optic connector can offer higher density and performance in many different environments compared to other types of fiber optic connectors, which makes it a more popular choice for many applications. That is why uniboot fiber patch cables terminated with specially designed LC fiber optic connectors have been invented. With its unique structure, LC uniboot fiber patch cable has more advantages over traditional LC to LC cable in high density cabling environments. Differences between LC uniboot fiber patch cables and standard LC fiber patch cables are noticeable. The following picture shows an LC uniboot fiber patch cable (left) and a standard LC fiber patch cable (right) separately.

Less Cable Count to Cut Space Requirements

A traditional LC duplex fiber patch cable usually uses a two-cable design with two fibers separately enclosed in two different cables, and it is terminated on each end with a standard duplex LC fiber optic connector. LC uniboot fiber patch cable uses only one cable even it has two fibers. It has a single boot at the back of the duplex LC fiber optic connector. Two fibers for duplex transmission are firmly enclosed in a single cable, which can cut down the cable count up to 50% compared with traditional LC duplex fiber patch cords. Space requirements of data center cabling can be reduced significantly by LC uniboot fiber patch cables.

Easier Polarity Reversal to Increase Efficiency

For LC duplex fiber patch cables, polarity change can be really inconvenient, especially in high density cabling environments like data centers. Additional tools and fiber cable re-termination are usually required to change polarity of traditional LC duplex fiber patch cables, which wastes both time and money. And sometimes, improper handling could result in various faults. But the polarity reversal for LC uniboot fiber patch cables is much easier, which can be easily changed by several simple steps without additional tools. Currently, there are several different versions of LC uniboot fiber patch cables, and the polarity reversals of them might differ from each other. Two commonly used versions of LC uniboot fiber patch cables polarity reversal steps are shown in the following picture.

Special Feature to Achieve More Possibilities

With LC uniboot fiber patch cables, fiber optic network design can be more flexible without worrying about spaces and polarity problems. Other than space-saving and easy polarity reversal, LC uniboot fiber patch cable can also achieve more possibilities with its great features. Fiber optic cabling provides faster speeds with reliable quality, which saves a lot of time and money. And, the design and improvement of uniboot fiber patch cables have never stopped. LC uniboot fiber patch cable with push-plug tab has already been available in the market. This little change can make easier finger access and quicker latch release available, and it can also help to connect or disconnect a single fiber patch cable without affecting other surrounding links.

Conclusion

LC uniboot fiber patch cable can help solve problems in high density cable management with high efficiency. It is a more favorable solution compared to standard LC fiber patch cable. LC uniboot fiber patch cable can cut down fiber cabling spaces up to 50% and provide much easier polarity reversal solution. Different kinds of LC uniboot fiber patch cables are available for your applications, such as different cable lengths, different fibers and different cable jackets. You can choose the right one for your needs.

What Are Simplex, Half Duplex and Full Duplex?

When talking about fiber optic jumper cables, such as LC LC multimode duplex fiber cable or LC SC single-mode simplex fiber optic patch cable, we came across simplex and duplex, or full duplex. What are simplex and full duplex? They are two kinds of communication channels in telecommunications and computer networking, which provide pathways to convey information. In fact, other than simplex and full duplex, there is another communication channel named half duplex. These three communication channels are commonly used in telecommunication networks.

A communication channel can be either a physical transmission medium or a logical connection over a multiplexed medium. The physical transmission medium refers to the material substance that can propagate energy waves, such as wires in data communication. And the logical connection usually refers to the circuit switched connection or packet-mode virtual circuit connection, such as a radio channel. With communication channels, information can be transmitted without obstruction. In this article, a brief introduction to these three communication channel types will be given.

Simplex

A simplex communication channel only sends information in one direction. For example, a radio station usually sends signals to the audience but never receives signals from them, thus a radio station uses a simplex channel. And it is also commonly used in fiber optic communication. One strand is used for transmitting signals or for receiving signals. The good part of simplex mode is that its entire bandwidth can be used during the transmission.

Half Duplex

In half duplex mode, data can be transmitted in both directions on a signal carrier but not at the same time. At a certain point, it is actually a simplex channel whose transmission direction can be switched. Walkie-talkie is a typical half duplex device. It has a "push-to-talk" button which can be used to turn on the transmitter but turn off the receiver. Therefore, once you push the button, you cannot hear the person you are talking to but your partner can hear you. An advantage of half-duplex is that the single track is cheaper than the double tracks.

Full Duplex

A full duplex communication channel is able to transmit and receive data in both directions on a signal carrier at the same time. It is constructed by a pair of simplex links that allows bidirectional simultaneous transmission. Take telephone as an example, people at both ends of a call can speak and be heard by each other at the same time because there are two communication paths between them. Thus, using the full duplex mode can greatly increase the efficiency of communication.

Simplex Fiber Optic Cable vs. Duplex Fiber Optic Cable

A simplex fiber optic cable has only one strand of tight-buffered fiber inside the cable jacket for one-way data transmission. The aramid yarn and protective jacket enable the cable to be connected and crimped to a mechanical connector. It can be used for both multimode and single mode patch cable. For instance, single-mode simplex fiber optic cable is suitable for networks that require data to be transmitted in one direction over long distance. Different from simplex fiber optic cable, duplex fiber optic cable has two strands of fibers constructed in a zipcord style. It is often used for duplex communication between devices to transmit and receive signals simultaneously. Duplex fiber optic cable can be applied to all sorts of applications, such as workstations, fiber switches and servers, fiber modems and so on. And single-mode or multimode cable is also available with duplex cables.

Conclusion

To understand the operation of networking, you should at least know the concept of communication channels. Simplex, half duplex and full duplex are three modes of communication channels. Each one can be deployed for different applications. To make a cost-effective decision, you can choose the right fiber optic cable according to the channel mode that you need.

Solution for Fiber Patch Cable Bending

When you install fiber optic jumper cables, you should not bend them beyond their bend radius, for light may "leak out" when the fiber is bent. To install fiber optic jumper cables in tight spaces of high-density fiber patching areas in data centers, more cable bending are inevitably needed. As the fiber bends more acutely, more light leaks out (shown in the picture below). How to solve this problem? The answer is bend insensitive fiber patch cable. Bend insensitive fiber patch cable exhibits much lower optical power loss under bend conditions while remaining compatible with conventional cabling. What is bend insensitive fiber patch cable? This post will talk about this solution.

What Is Bend Radius?

To understand bend insensitive fiber patch cable, first you need to what bend radius is. Bend radius is the minimum radius one can bend a pipe, tube, sheet, cable or hose without kinking it, damaging it, or shortening its life. The smaller the bend radius is, the greater is the material flexibility. When installing fiber optic jumper cables, you need to be careful enough not to exceed the cable bend radius. Usually, if no specific recommendations are available from the cable manufacturer, the cable bend radius should be 20 times smaller than the cable's outside diameter when pulling the cable and 10 times the outside diameter when lashed in place. For example, while pulling a 2mm diameter cable, only a 40mm sweep is allowed; when lashed in place, make sure it's a 20mm sweep. For most of today's fiber patch cables, the bend radius is 30 mm. As we know, there are single-mode patch cable and multimode patch cord, and accordingly there are single-mode bend insensitive fiber patch cables and multimode bend insensitive fiber patch cables. These two kinds of bend insensitive fiber patch cables will be introduced below.

Single-mode Bend Insensitive Fiber Patch Cable

Single-mode bend insensitive fiber patch cables have been commercially available for a few years. ITU recommendation G.657 specifies two classes of single-mode bend insensitive fiber patch cables: G.657 A and G.657 B. Each category (A and B) is then divided into two sub-categories: G.657.A1, G.657.A2 and G.657.B1, G.657.B2. The minimum bend radius of G.657.A1 fibers is 10 mm, G.657.A2 and G.657.B1 fibers is 7.5 mm and G.657.B2 fibers is 5 mm. G.657.A1 and G.657.A2 fibers are fully compliant with ITU-T G.652.D fibers. Compared with minimum bend radius of the standard single-mode G.652 fibers, which is usually 30 mm, G.657 single-mode bend insensitive fiber patch cables are much more flexible, which thus can be confidently installed with a variety of installation methods and in the increasingly high-density application spaces of today's data center.

Multimode Bend Insensitive Fiber Patch Cable

Multimode bend insensitive fiber patch cables with a minimum bend radius of 7.5mm compares very favorably to the 30mm bend radius traditionally specified. To achieve this, an optical "trench" is added to the cladding area outside of the fiber core. This trench retains most of the light that would have escaped the core of a traditional multimode fiber. Requirements for a tighter bend radius have been developed based primarily on factors in the FTTH (fiber to the home) market. However, the benefits for premise markets have rapidly become apparent, particularly in data centers where more and more fibers are being installed in smaller areas. The expectation is that this new feature can enable deployment of multimode fibers in higher densities.

Conclusion

Bend insensitive fiber patch cables are made with solid trench which assists fiber optic cable to reduce optical loss when the cable is bent. They provide the same high quality, mechanical features and optical performance as standard fiber patch cords with the added capability of maintaining optical performance when bent or flexed. Bend insensitive fiber patch cables are available for multimode (OM2, OM3 and OM4) and single-mode (OS2) networks. Whether to choose single-mode bend insensitive fiber patch cables or multimode bend insensitive fiber patch cables, you can make a decision based on your applications.

Direct Attach Cable Assemblies for Data Center Interconnection

As direct attach cable assemblies use the same port as optical transceivers, but with significant cost savings and power savings in short reach applications, they are becoming more and more popular among data center operators. Direct attach cable assemblies are mainly used as media to support high transfer rates between servers, switches and storage devices in data centers. In this post, we will talk about usage of direct attach cable assemblies for data center interconnection.

Types of Direct Attach Cable Assemblies

Direct attach cable assemblies are terminated with transceiver-style plugs, such as SFP+ (enhanced small form-factor pluggable), SFP28, QSFP+ (quad small form-factor pluggable), QSFP28, and CXP, etc. Using the same port as transceiver optics, direct attach cables can support Ethernet, Infiniband and Fibre Channel but with independent protocols. In general, direct attach cable assemblies are divided into three families—direct attach passive copper cable, direct attach active copper cable and active optical cable (AOC).

Passive Direct Attach Copper Cable

Passive direct attach copper cables are without active circuitry component. They can achieve interconnections up to 7m at 10 Gbps or 40 Gbps with low power. Direct attach passive copper cable assemblies, like HP J9281B SFP+ passive direct attach copper cable, offer high-speed connectivity between equipment. They are compatible with hubs, switches, routers, servers, and network interface cards (NICs) from leading electronics manufacturers like Cisco, Juniper, etc.

Active Direct Attach Copper Cable

Active copper cables are designed in the same cable type as the passive one, but they contain low power circuitry in the connector to boost the signal and are driven from the port without additional power requirements. The active version provides a low cost alternative to optical transceivers, and are generally used for end of row or middle of row data center architectures for interconnect distances of up to 15 meters.

Active Optical Cable

Active optical cable (AOC) incorporates active electrical and optical components. It can achieve longer distance than the copper assemblies. In general, active optical cable can reach more than 100m via multimode fiber. Compared to direct attach copper cable, AOC, like Cisco SFP-10G-AOC10M SFP+ AOC, weighs less and can support longer transmission distance. It is immune to electromagnetic energy since the optical fiber is dielectric (not able to conduct electric current). And it is an alternative to optical transceivers and it can eliminate the separable interface between transceiver module and optical cable. However, it costs more than copper cable.

In addition, with the fan-out technology, both direct attach copper cable and active optical cable can be designed as breakout direct attach cable assemblies, like 40G QSFP+ to 4x10G SFP+ AOC, which can better satisfy the demands on network migration.

Direct Attach Cables for Data Center Interconnection

Direct attach cable assemblies are ideal choices for short-reach direct connection applications. Generally, they are used in the EDA (Equipment Distribution Area) where cabinets and racks house end equipment (servers) and where horizontal cabling from the HDA (Horizontal Distribution Area) are terminated at patch panels, as shown in the following picture:

For interconnection in racks and between rows of racks, direct attach cable assemblies are used to connect server to switch, storage to switch or switch to switch. Depending on different interconnect applications and distance requirements, direct attach copper cables, passive or active, active optical cable, or breakout direct attach cable assemblies with various length options can be used.

As 10G network is widely deployed in today's data center, 10G SFP+ DACs are commonly used in interconnect applications below 15m, such as server to switch or storage to switch interconnection in the same rack. And now 25GbE is popular and 25G direct attach cable assemblies, such as SFP28 DACs, are already available in the market. For 40GbE, 40G QSFP+ DACs and AOCs are used. Of course, higher speed and more bandwidth are needed for spine switches. Thus, 100G DACs, like QSFP28 DACs are used in this case.

Conclusion

There are a wide range of direct attach cable assemblies, including both direct attach copper cable assemblies and active optical cables which cover data rates of 10G, 25G, 40G, 100G and 120G. You can choose SFP+ direct attach cables for your 10G networks, or QSFP+ direct attach cables for your 40G networks. And both copper and optical fiber options are available.