Fiber Patch Cable Selection Guide for 40G QSFP+ Transceivers

Upgrading the existing system to 40G network can be a tough and complicated task since there are considerable amount of factors to plan and design. Whether the switches are capable of supporting such a high speed Ethernet? What kind of optical transceiver works best on the switches? Which optical transceiver is more cost-efficient? 40G QSFP+ transceiver (Quad Small Form-factor Pluggable transceiver) are considered to be the most economical and effective transceiver solutions for 40G migration. The selection for fiber patch cords for interconnection is vital as well.

Patch Cords Matter to 40G

To successfully build 40G transmission network, the switches need to be connected together. In this case, patch cords are usually linked to fiber optic transceivers which are plugged in Ethernet switches (as shown in the following picture), thus to accomplish connections between these switches. The quality of these connections can largely affect the reliability and stability of the whole 40G network. However, connectivity of 40G is much more complex than ever. Thus selecting the proper fiber patch cables for 40G network is more difficult and becomes a critical issue in 40G migration. It is known that QSFP+ transceivers are suggested for 40G, and this article will provide some detailed information about fiber patch cable selection for 40G QSFP+ transceivers.

Selecting Patch Cords for 40G QSFP+ Transceivers

Patch cords selection is a big issue to 40G not only because the switch connections necessity, but also because of the transmission principle of the fiber optic signals and the high density trend of 40G transmission. Several important factors should be taken into account when selecting patch cords for 40G QSFP+ transceivers, which are cable type, connector type and switch port.

Cable Type

Performances of optical signals often vary from different wavelengths. Even optical signals with the same wavelength perform totally different when they run through different fiber optic cables. Thus, the selection of the cable type is essential.

A typical question that frequently asked when buying fiber optic patch cords for 40G QSFP+ transceiver can illustrate this point clearly. Can a 40GBASE universal QSFP+ transceiver working on wavelength of 850 nm be used with OM1 patch cords? The answer is yes, but not suggested. As the optical signal transmission distance gets shorter as the data rate increases, the transmission distance and quality would be limited by using OM1 patch cords with 40G QSFP+ transceiver. OM1 cable is only suggested for 100Mb/s and 1000Mb/s transmission. Two upgraded cables—OM3 and OM4 are suggested for 40G QSFP+ transceivers in short distance.

IEEE has announced standards for 40G transmission in both long distance and short distance, which are 40GBASE-SR4 and 40GBASE-LR4(SR stands for short-reach and LR stands for long reach). The 40GBASE-LR4 is suggested for 40G transmission over single-mode fiber in long distance up to 10 km. Whereas the 40GBASE-SR4 is for 40G transmission in short distance over multimode fiber—OM3 (up to 100 meters) and OM4 (up to 150 meters). OM3 and OM4, which are usually aqua-colored, are accepted economical solutions for 40G in short distance with lower insertion loss and higher bandwidth.

Connector Type

The connector type of the patch cords depends on the interface of 40G QSFP+ transceiver. Currently there are two interfaces commonly adopted by 40G QSFP+ transceiver, which are MPO and LC. Usually 40G QSFP+ transceiver with MPO interface is designed for short transmission distance and LC for long transmission distance. However, several 40G QSFP+ transceivers like 40GBASE-PLR4 and 40GBASE-PLRL4 have MPO interfaces to support long transmission distance.

High density is the most obvious features of 40G transmission, which is largely reflected in the MTP connectors on patch cords used with 40G QSFP+ transceiver. As QSFP+ transceiver uses four 10G channels to achieve the 40G transmission, thus 4 pairs of fibers are used and the 12-fiber MTP connectors can provide a time-saving and stable solution for 40G QSFP+ transceivers. However, for multi-fiber connection, polarity should be considered for the selection of the patch cord.

However, to meet the market demands, 40G QSFP+ transceiver with LC interface is also available. This type of QSFP transceiver uses four lanes with each carrying 10G in 1310nm window multiplexed to achieve 40G transmission. For this type, patch cable with duplex LC connector should be used.

Switch Port

Network flexibility becomes more crucial as the speed of Ethernet increases. When it comes to 40G, network flexibility becomes an urgent issue which is closely related to applications. Right selection of patch cords for 40G QSFP+ transceiver can increase the network flexibility significantly and effectively. Here offer two most common examples in 40G applications: 40G QSFP+ to 40G QSFP+ cabling and 40G QSFP+ to SFP+ cabling.

For 40G QSFP+ to 40G QSFP+ cabling:

1. For distance up to 100 m, the 40GBASE-SR4 QSFP+ transceiver can be used with OM3 fiber patch cable attached with a MPO on each end.

2. For distance up to 150 m, the 40GBASE-SR4 QSFP+ transceiver can be used with OM4 fiber patch cable attached with a MPO on each end.

3. For distance up to 10 km, the 40GBASE-LR4 QSFP+ transceiver can be used with single-mode fiber with LC connectors. The picture above shows the transmission of 40GBASE-LR4 QSFP+ transceiver with LC connector over single-mode fiber.

It’s very common that 40G ports are needed to be connected with 10G port. In this case, fan out patch cable with MTP connector on one end and four LC duplex connectors on the other end is suggested (as shown in the picture below).

Conclusion

Fiber optic patch cords hold an essential position in connecting and accomplishing the whole 40G transmission network. When selecting the right patch cable for 40G QSFP+ transceiver, cable type, connector type and switch port should be taken into consideration, since these three factors are closely relevant to transmission distance, network flexibility and reliability of the whole 40G network. What we discussed above simply offers you a reference guide. For professional and cost-effective network design as well as 40G products, please visit www.fs.com.

First published: http://www.fiber-patch-cords.com/blog/a/133/Fiber-Patch-Cable-Selection-Guide-for-40G-QSFP+-Transceivers

Basics of Mode Conditioning Patch Cable

The 802.3z standard (IEEE) for Gigabit Ethernet over optical fiber was released to satisfy the demand for higher bandwidth. While 1000BASE-LX transceiver modules can only operate over single-mode fibers. Then what if the transceiver must be employed over both single-mode and multimode fibers? The problem of differential mode delay (DMD) occurs when single-mode fiber is launched into a multimode fiber—it will generate multiple signals that confuse the receiver and lead to inevitable errors. If you ever encounter such a problem, a mode conditioning cable is much needed to help. This article is about some rudiments of mode conditioning cable.

What Is Mode Conditioning Patch Cable?

Mode conditioning patch cable functions the same way as a standard patch cable, however, its mode-conditioning unit consists of a cable assembly with an offset single-mode fiber to multimode fiber connection point and duplex connectors on each end. It is basically a duplex multimode cable that has a small length of single-mode fiber at the start of the transmission length. With two multimode fibers on one end and one multimode and one single-mode fiber on the other end. The mode-conditioning patch cord is suitable for long-wavelength multimode applications like Gigabit Ethernet.

How Does Mode Conditioning Patch Cable Work?

The basic working principle of mode conditioning patch cable is that, the launch of the light coming out of the equipment begins on a single-mode fiber, and the single-mode fiber is precision fusion spliced to the multimode fiber to a precise core alignment (see picture below). The light is launched on to the multimode fiber at a precise angle, giving the cable its mode conditioning properties.

By using an offset between the single-mode fiber and the multimode fiber, mode conditioning patch cords eliminate DMD effectively. And the resulting multiple signals make it possible to use 1000BASE-LX transceivers over multimode fiber systems. This is considered to be a cost-effective and energy-saving solution since there is no need to upgrade the whole fiber plant.

Tips for Using Mode Conditioning Patch Cable

Mode conditioning patch cables are available from various vendors on the market, so it is important to know where and when they should be used.

1.Mode conditioning cable is normally used in pairs. That means that you will need this cable at each end to connect the equipment to the cable plant. So then, these cables are usually ordered in even numbers. The usual reason why someone may order one cable is so they may keep it as a spare.

2.If your Gigabit Lx switch is equipped with SC or LC connectors, be sure to connect the yellow leg (single-mode) of the cable to the transmit side, and the orange leg (multimode) to the receive side of the equipment. It is imperative that this configuration be maintained on both ends. The swap of transmit and receive can only be done at the cable plant side. (see the picture below)

3.Mode conditioning patch cords can be only used for single-mode to multimode conversion. If you want to convert multimode to single-mode, then a media converter will be required.

Mode Conditioning Patch Cable Installation

Looking at the mode conditioning cable assembly in the following picture, we can see that the fusion splice is protected by a black over-wrap. On the left side there is an orange and a yellow cable, and this is the side of the cable that connects to the gigabit equipment, with the yellow single-mode leg to be connected to the transmit side.

Here we provide some steps to follow when installing mode conditioning patch cable:

• Step1: Connect the yellow leg (single-mode connector) of the cable into the transmit bore of the transceiver.
• Step2: Connect the rest orange legs (multimode connectors) of the cable into the receive bore of the transceiver.
• Step3: At the other end of the patch cord, put all the orange legs (multimode connectors) into the patch panel.
• Step4: Repeat the above three steps for the second transceiver located at the other end of the network link.

Conclusion

Mode conditioning patch cable offers an optimum solution for improving data signal quality and increasing transmission distance. It is available with various options of different connectors, jackets and lengths. Hope this article could provide you some useful information and constructive suggestions.

First published: http://www.fiber-patch-cords.com/blog/a/131/Basics-of-Mode-Conditioning-Patch-Cable

Fiber Jumper Endface Inspection and Cleaning Methods

Fiber optic communications have not only eliminated the vast majority of previous network limitations, but also expanded the capabilities of networks beyond expectations. Fiber jumper, known as fiber patch cable as well, serves as an indispensable component in data transmission. So it is critical that the fiber jumper endfaces are clean and free from particular contamination to assure proper performance and reliability of the whole network systems, which absolutely make for successful operation. Then, have you ever encounter problems when performing fiber jumper cleaning? Take it easy, this article will offer you an instructive guideline to deliver better fiber jumper inspection and cleaning.

Fiber Jumper Overview

Fiber jumper is a fiber optic cable terminated with fiber optic connectors on both ends. It is often used to connect optical transceiver and fiber terminal box. Basically, it can be divided into single-mode patch cable (OS1, OS2) colored yellow, and multimode patch cable (OM1, OM2, OM3, OM4) colored orange or grey. According to the terminated connector, it can be same connector type patch cable, like LC to LC fiber patch cable, or hybrid fiber patch cable with different connectors on each end, such as LC to SC fiber patch cable. Fiber jumpers are featured by low insertion loss and high return loss, good repeatability and good interchange as well as excellent environmental adaptability. They are most employed to computer work station to outlet and fiber optic patch panels or optical cross connect distribution center.

Ways to Inspect Fiber Jumper

There is no doubt that a well-performed fiber jumper is able to ensure high quality system connection, reduce network failure and identify the point of failure. And to achieve a better connection between fiber jumper and fiber coupler, the endface cleanliness of fiber jumper really matters since it directly affects the quality of network communications. There are also two ways to inspect the circumstances of fiber jumper endface.

Visual Inspection: Under normal circumstances the most common practice is to check the face dirt: disconnect the device and pick up the fiber jumpers against the light, by observing the side facing the bright light refraction to detect whether the end is clean and smooth. Through observation, if the side facing the light reflection is smooth and bright, then it is clean. if the side facing the light reflection is not too bright and not enough smooth, maybe there is dirt or there are scratches on the face. The endface of fiber jumper will seriously affect the quality of the optical transmission.

Instrument Checks: Among fiber jumper endface inspection tools, fiber optic microscope is the most widely used professional inspection equipment. When used in multimode fiber jumper, the microscope shows that ratio of 200 times, whereas used in single-mode fiber jumper, it shows that ratio of 400 times. With more advanced fiber optic microscope currently available on the market, one can test fiber jumper endface without disconnecting the equipment, meanwhile, it also avoids the risk of laser hurting eyes.  

Fiber Jumper Cleaning Methods

During the process of checking fiber jumper endface, contamination must be properly cleaned and removed to ensure high quality data link and communication. Since cleaning methods can vary from different maintenance personnel and circumstances, cleaning effects hence are not the same. However, if the conditions permit, it is advised to use professional cleaning tools to deliver better cleaning.

Cleaning Without Professional Tools

1. Clean cotton ball in one hand, and then ethanol drops on cotton balls.

2. With anhydrous alcohol cotton ball wiping down with the same direction, according to the severity of the end surface dirt.

3. Put a good face with an alcohol wipe three or more layers of the folded lens paper, to wipe face in the same direction until the alcohol is completely dry and the endface of the light reflection of bright reflective so far.

4. Carefully check the condition of the local light reflex face each and end face on fiber debris residues, if necessary, repeat the above step 1 to 3 until the end face clean and flawless.

Cleaning With Professional Tools

Here, we introduce the clean endface card to help clean the fiber jumper endface.

1. Tear plastic coverage on the cleaning belt.

2. Drop small drops of detergent to the cleaning belt.

3. Holding the fiber connector with the vertical direction, wipe from the wet to the dry.

4. Check again to ensure clean completely. If necessary, use a cleaner to clean it again according to the above steps.

Conclusion

As the fiber jumper is considered to be a vital component in fiber optic network, more importance should be attached to its performance and cleanliness. The inspection and cleaning method we offer are simple and feasible to conduct, besides, the routine operation and maintenance are also essential. After all, only these details are taken seriously, can a reliable and flexible communication environment be assured.

First published: http://www.fiber-patch-cords.com/blog/a/130/Fiber-Jumper-Endface-Inspection-and-Cleaning-Methods

Upgrading Your Network With OM3/OM4 Patch Cable

As the demand for higher speed, reliability, manageability and flexibility of the network never ends, it is high time to upgrade your existing infrastructure in data centers. Therefore, more attention should be attached to fiber patch cable—one of the most vital components to ensure sound network environment. Currently, two types of multimode fibers—OM3 and OM4 patch cables have provided optimum choices to enhance network reliability and performance, which will be explained detailedly in following paragraphs.

OM3 and OM4 Patch Cable Overview

OM here refers to optical multimode, and multimode fiber has been widely employed in data centers nowadays since it presents a cost efficient option for short distance transmission. OM3 and OM4 are both laser-optimized multimode fibers with 50/125um core, which are designed for use with 850nm VCSELS (vertical-cavity surface-emitting laser) and are developed to accommodate faster networks such as 10, 40 and 100 Gbps. Compared with OM1 and OM2 patch cables, OM3 and OM4 patch cables are undoubtedly more suitable for today’s demanding networks as they enable data to transport at higher rate and longer distance. The following diagram clearly illustrates the performance of different multimode patch fiber.

Fiber Type	1G	10G	40/100G
OM1	300 m	36 m	N/A
OM2	500 m	86 m	N/A
OM3	1 km	300 m	100 m
OM4	1 km	550 m	150 m

The Advantages of OM3 and OM4 Patch Cable

The IEEE 802.3ba 40/100G Ethernet Standard was ratified in June 2010, which provides specific guidance for 40/100G transmission with multimode and single-mode fibers. According to the standard, OM3 and OM4 are the only multimode fibers included in it. And they are massively applied to upgrade the legacy infrastructure, especially for migrating to high-density networks. So, how can we exactly benefit from OM3/OM4 patch cables?

Get Higher Bandwidth

First and foremost, bandwidth is the main reason why OM3 and OM4 patch cables are used for network upgrades. OM3 and OM4 patch cables are optimized for 850nm transmission and have a minimum 2000 MHz∙km and 4700 MHz∙km effective modal bandwidth (EMB). Compared with OM1 and OM2 patch cables with the maximum 500 MHz∙km, advantages of OM3 and OM4 are obvious. With a connectivity solution using OM3 and OM4 cables that have been measured using the minimum EMB calculate technique, the optical infrastructure deployed in the data center will meet the performance criteria set by IEEE for bandwidth.

Get Longer Transmission Distance

The impact that transmission distance of fiber patch cables has on the data center cabling cannot be overestimate. And the manageability and flexibility will increase parallelly with longer transmission distance. OM3 and OM4 patch cables can support longer transmission distance compared with traditional multimode fibers. Generally OM3 fibers can run 40/100 Gigabit at 100 meters and OM4 fibers can run 40/100 Gigabit at 150 meters.

Get Lower Insertion Loss

Insertion loss has always been an essential factor to be considered during data center cabling. This is because the total connector loss within a system channel impacts the ability to operate over the maximum supportable distance for a given data rate. As total connector loss increases, the supportable distance at that data rate decreases. OM3 patch cable is specified to a 100m distance with a maximum channel loss of 1.9dB, which includes a 1.5dB total connector loss budget. And OM4 patch cable is specified to a 150m distance with a maximum channel loss of 1.5 dB, including a total connector loss budget of 1.0 dB. In this way, OM3 and OM4 patch cables help to achieve maximum flexibility and longer supportable transmission distance.

OM3 Patch Cable vs. OM4 Patch Cable

Apparently, OM3 and OM4 patch cables offer us an ideal alternative to upgrade the existing infrastructure. A question may occur to us is to determine which one is better. Well, it depends on several factors. Among which the applications and the total costs always serve as major ones.

Owing to the difference in the construction of fiber cable, OM4 patch cable has better attenuation and higher bandwidth of longer distance. Moreover, the cost for OM4 is higher than OM3. As 90% of all data centers have their runs under 100 meters, OM3 may be a better choice. However, considering future growth, the overall cost would come down with the increasing demand. In this case, OM4 might be the most viable option.

Conclusion

With either OM3 or OM4 patch cable, you are capable of upgrading the existing infrastructure to achieve more reliable and flexible network performance. Since they both provide us higher bandwidth, longer transmission distance and lower insertion loss. And when choosing between these two types of patch cables, your decision better be based on the current circumstances of the application and budget. Moreover, don’t forget to take future plan into consideration.

First published: http://www.fiber-patch-cords.com/blog/a/129/Upgrading-Your-Network-With-OM3/OM4-Patch-Cable