The New 10G Multimode Optical Solution – 10GBASE-LRM

10 Gigabit Ethernet has been applied for a long time in data centers and enterprise LANs. For 10G Ethernet connection, there are both single-mode and multimode solutions. First let’s see the original multimode solutions and supportable distances for 10G Ethernet.

10GBASE-S operates at 850nm wavelength. It can support up to 300m distance over laser-optimized OM3. This makes it a popular standard for data centers and cooperate backbones. For the conventional OM1 and OM2 which are not optimized for laser transmission, the furthest supportable distance is 33 m and 82 m. So these two solutions are only used in equipment rooms or small data centers.

10GBASE-LX4 was specified to support 300 m over three cable types. So it relies on coarse wavelength division multiplexing (CWDM) which is more complex and expensive technology. 10GBASE-LX4 operates at 1300nm wavelength and that requires additional cost on mode-conditioning patch cords (MCPCs).

The high cost and relatively slow adoption of 10GBASE-LX4 drive the development of a new standard—10GBASE-LRM. 10GBASE-LRM is developed to offer a longer reach for conventional fiber cables at a lower cost and smaller size than 10GBASE-LX4. The following will talk about 10GBASE-LRM from three sides.

Transmission Distance

On condition the supporting distance, 10GBASE-LRM can only support 220 m. It’s suitable for LAN networks within buildings. But a cabling survey provides that for 10G network, the distance is not able to address 30% of in-building channels.

Electronic Dispersion Compensation

The key to the long reach of 10GBASE-LRM on conventional multimode fiber is electronic dispersion compensation (EDC). EDC is deployed as an integrated circuit that acts like a complex filter on the received signal from the optical fiber. The purpose is to extend the maximum supportable distance. 10GBASE-LRM applies EDC technology and is therefore independent of the optical wavelength. 10GBASE-LRM operates at 1300 nm.

EDC chips is added to a linear detector in the receiver. As an additional component, it increases cost, consumes power and wastes heat. It can only work as intended in conjunction with a linear detector and amplifier. Because the EDC device must operate on a faithful analog rendition of the optical waveform in the fiber. For 10GBASE-LRM, to reproduce the optical waveform with precision, extra requirements and cost on the receiver design are needed.

Multiple Transmit Launch Conditions

In order to improve the chances of operating at a higher bandwidth, 10GBASE-LRM relies on multiple transmit launch conditions.

One launch is achieved by using mode-conditioning patch cord. The other launch is produced using a regular multimode patch cord. Through the two launches, different modes can be achieved and a favorable operating condition can be easily found.

There are four possible patch cord combinations at both ends of the channel. The preferred launch uses MCPCs on both ends. This process requires a test for link stability for each configuration. The user should shake and bend the patch cord at the transmit end while observing channel health indicators at the receive end. The shaking and bending of the cords causes changes to the received waveform which the receiver must tolerate in normal operation. If there were transmission errors, then users should change another launch. The errors indicate that the channel is operating near or beyond the limit of the receiver’s capability and the link may fail in operation.

However, the 10GBASE-LRM standard’s committee refuse to implement this channel test. So the burden of the shaking and bending lies on the users. It’s not good for the popularity of 10GBASE-LRM.

Comparison of Several 10G Transceivers Cost

The following will compare the cost of 10G transceivers from several sides, including laser, receiver, package and cords.

Laser: 10GBASE-LRM uses 1310nm fabry perot lasers, which cost fewer than 10GBASE-L’s and 10GBASE-LX4 DFB lasers, but more than 10GBASE-S’s 850nm VCSELs. 10GBASE-LRM requires tighter transmitter waveform control to limit the transmit waveform dispersion penalty that EDC can’t compensate. Thus, it reduces transmitter yields and increases cost.

Receiver: 10GBASE-LRM adds EDC chip cost to receiver and needs a linear detector and amplifier instead of other cheap digital equipment.

Package: 10GBASE-LRM requires a smaller package than 10GBASE-LX4. However, not like 10GBASE-S, 10GBASE-LRM requires higher-cost single-mode transmitter alignment for compatibility with mode conditioning patch cords.

Cords: 10GBASE-LRM needs mode conditioning patch cords for reliable link operation. And the cost is much higher than regular SMF or MMF fiber optic patch cords.

Through the comparison among these 10G optical transceivers, you may find which one costs fewer. 10GBASE-LRM transceiver is cheaper than 10GBASE-LX4, more expensive than 10GBASE-L and 10GBASE-S transceivers.

Conclusion

10GBASE-LRM is a multimode solution for 10 Gigabit Ethernet. Based on the above content, 10GBASE-LRM has some advantages over 10GBASE-LX4. It offers lower cost and smaller package. But the distance and reliability are not very ideal. Compared with 10GBASE-S, 10GBASE-LRM is not so good as to the cost, simplicity, reliability and distance capability. FS.COM provides various types of cost-effective 10GBASE transceivers, such as 10GBASE-LR, 10GBASE-SR, 10GBASE-ER, etc. Other compatible brands like Cisco, Juniper, Arista, Brocade are also available. Among so many choices, you must choose the most suitable solution for your network connection.

Originally published at www.fiber-optic-equipment.com

10GBASE-LRM vs. 10GBASE-LX4, Which One Wins?

For 10 Gigabit data transmission, various physical-layer interconnects are available, such as 10GBASE-LX4, CX4, SR, LR and ER as well as 10GBASE-LRM. With so many options, you may be confused which one is the best. This article will discuss two options requiring for multimode fiber cable. They are standards LX4 and LRM. Which one do you think is better?

10GBASE-LX4

Now maybe 10GBASE-LX4 is not so popular. But it’s not the same case several years ago. This standard is the first optical interface standard developed to run at 10 Gbits/sec over multimode optical fiber backbones in vertical risers. LX4 was robust and stable. Many vendors have produced LX4 related equipment. Once there was an industry trade group—the LX4-TG (LX4 Trade Group) formed to promote LX4 technology.

10GBASE-LRM

Later, the LRM standard is developed by the same IEEE group that generated the LX4 standard. The specifications can only support the distance of 220 m. At first, technicians intended to stretch the coverage to be 300 m. However, it’s too risky and limited the ability to release the standard in a timely manner. The reduced distance is good for more robust LRM operation, but may limit the product’s applications in some building backbones.

Performance of 10GBASE-LX4 and LRM

LX4 module can be used for both single-mode or multimode fiber connection with distance up to 10 km and 300 m. LX4 applies CWDM technology using four wavelength—transmitters near 1300 nm, a CWDM multiplexer and demultiplexer, and four receivers. The advantage of this approach is that the transmitters and receivers are all operating at about one-quarter of the data rate; so the data transmission is robust to modal dispersion. But it has the disadvantages of high cost, big size and non-manufacturability.

While LRM uses wavelength of 1310 nm with a single transmitter and a receiver with an adaptive electronic equalizer IC in the receive chain. LRM module has a simpler optical path. The laser of LRM module can be a distributed-feedback (DFB) laser, a vertical-cavity surface-emitting laser (VCSEL), or a Fabry-Perot (FP) laser. Both DFBs and VCSELs provide a very clean, single-wavelength output, which minimizes signal degradation due to spectral effects. And an FP laser source can produce a range of different wavelengths. Different wavelengths travel through the fiber at slightly different speeds, creating additional jitter which will be recovered by the EDC known as adaptive equalization technology. EDC is used to compensate for the differential modal dispersion (DMD) present in legacy fiber channels.

Advantages of LRM

The LRM approach has three key advantages over LX4. The following will give an introduction from three sides.

Size — LX4 uses four lasers and laser drivers and four photodiodes and preamplifiers, which makes LX4 module a big size. But LRM uses the same optical component footprint as other 10G modules, with EDC functionality.

Cost — LRM devices cost less than LX4 equipment. From the point of manufacturing yields and packaging and assembly cost, the price of LX4 is higher than that of other short reach 10G modules. By contrast, LRM substitutes low-cost silicon for the optical complexity of LX4. So it greatly reduces the cost.

Assembly — LX4 requires a significant amount of assembly (splicing, fiber attach and routing, and in some cases multiple personal computer boards, flex cables, etc.). Thus it naturally reduces yields at the module level and makes the module difficult to be manufactured. However, LRM requires no extra assembly compared with existing 10G SR or LR modules.

Conclusion

LX4, as the first standard developed for 10GBASE data rate over multimode fiber backbones, has its special significance in the fiber optic communication history. As technology is continuously developing, so better objects will be created and replace the not so good ones. LRM is another standard for 10GBASE. It turns to be more popular with its smaller size, lower cost and greater manufacturability. So 10GBASE-LRM SFP+ is a good choice for your 10GBASE network. FS.COM offers Brocade 10G-SFPP-LRM compatible 10GBASE-LRM SFP+ 1310nm 220m DOM transceivers and other 10GBASE transceiver modules. Each transceiver has been tested on full range of Brocade equipment to keep 100% compatibility. Any service, please contact via sales@fs.com.

Originally published at www.fiber-optic-equipment.com

Brief Analysis on Fibre Channel Technology

Fibre Channel is a set of advanced data transport standards that allow large amounts of data to be moved at multi-gigabit speeds between computers, servers, and other devices. Fibre Channel is widely applied because its high bandwidth, proven reliability and some other benefits. This article will talk about Fibre Channel information.

“Fibre” and “Fiber”

You must be confused the name of this standard. Why is it called “Fibre Channel” instead of
“Fiber Channel”? The words “Fiber” and “Fibre” have the same meaning (“Fiber” is the international English spelling style, while “Fibre” is British style). “Fibre Channel” is the official spelling for the technology. “Fiber” just means the transmission media used in optical connections. The term “Fibre” is used by the Fibre Channel standard to refer to all the supported physical media types.

Fibre Channel Development History

Fibre Channel started in the late 1980s as part of the IPI (intelligent peripheral interface) to increase the capabilities of the IPI protocol. Fibre Channel was approved in 1988. The development of Fibre Channel standards serves as a model for the creation of modern transfer technology. From the beginning to its approval, it has gone through a number of iterations. Since it became more interoperable with other protocols and devices, it finally got the approval of American National Standards Institute (ANSI) in 1994.

At first, Fibre Channel was used in banks, large companies, and data centers. The installation is too complex especially when the transmitting media is optical fiber. But that bad situation has been changed. Today Fibre Channel seems to be a good choice for organizations with growing data storage needs.

Fibre Channel Benefits

Fibre Channel is more likely to be a high-speed switching system that interconnects local devices. Fibre Channel has the benefits of high speed, easy scalability, and attainable network lengths.

• High speed. Fibre Channel can provide consistent bandwidth of 2 Gbps or 4 Gbps. The rate is expected to double in a few years to 8 Gbps. It will meet the increasing needs of network users.
• Scalability. Fibre Channel networks perform with equal reliability, high rates, and flexible configuration. So it’s scalable up to thousands of ports even though device connections consist hundreds of integrated servers from different vendors.
• Guaranteed in-order delivery. Fibre Channel in-order delivery of raw block data. In-order delivery greatly boosts network efficiency. And some applications like video and IP streaming require this. Fibre Channel can naturally streams video frames in order, reducing bottlenecks that would degrade the video’s required speed per second.

Fibre Channel Deployment

A successful network deployment requires a lot. You must first know your needs and decide which type of Fibre Channel is the best suitable for your network. Is it a new network or an additional one? What’s the total physical length of the network? How many devices? To answer these questions, you may consider the cabling and connector type.

Cable — Copper or Fiber

It’s important to choose the right cable type for your network interconnection. To choose copper or fiber, it depends on the distances between the Fibre Channel devices being about to be connected.

Copper cable can be used for short distance. It’s typical in point-to-point and other topologies when devices are mounted in the same rack or are located in the same room. Copper cable is durable and can withstand being stepped on or pulled. It’s easy for installation and maintenance.

While, fiber optic cable is for long distance since the distance between devices become longer than before, maybe in different buildings or on different floors of a building. Compared to copper cable, fiber optic cable is immune to the electrical resistance and electromagnetic interference (EMI) which affect signals carried over copper cable. It can support higher data rates. But the problem is that the signal strength over fiber cable is easily to be damaged by the dirt, dust or other material defects in the fiber cable. So fiber optic testing is a must for high performance of the entire network. And much more cares and special tools are needed during fiber optic cable installation.

Connector

Nearly all Fibre Channel switches requires SFP transceiver modules. It’s very common to see 2G and 4G Fibre Channel SFP transceivers in the fiber optics market. For 2G and 4G FC SFPs, the interface is designed as “LC duplex”. When plug in LC patch cords, you should better avoid touching the end face of the connector to ensure the network work with long-term, consistent performance and reliability. If the cable is not preterminated, it will be more complex. You need to strip cable’s outer jacket and the fiber coating to attach the connector. All fiber optic connectors should be carefully tested after installation. If it’s possible, try to buy high quality and certified preterminated cables from reliable vendors.

Conclusion

Fibre Channel is a flexible, scalable, high-speed data transfer interface that can operate over both copper and fiber optical cable. FS.COM provides 2G and 4G Fibre Channel SFP transceivers which can support distance up to 80 km. All the transceivers have been fully tested. We also offer preterminated duplex LC patch cords for Fibre Channel deployment. For more detailed information, please contact via sales@fs.com.

Originally published at www.fiber-optic-equipment.com

FS.COM Cost-effective QSFP-40G-LX4 Transceiver

10Gbps data rate can’t meet the high-speed needs. So people start to develop 40Gbps solutions. As a result, a variety of 40G QSFP+ transceivers can be found in the market, like QSFP-40G-SR4, QSFP-40G-CSR4, QSFP-40G-LR4, QSFP-40G-LX4, etc. Different transceivers offer different ways to migrate from 10G to 40G. Among these solutions, which one is the most cost-effective? The answer is QSFP-40G-LX4. This following test will tell about QSFP-40G-LX4 in details.

QSFP-40G-LX4 Introduction

Juniper networks JNP-QSFP-40G-LX4 transceiver applies the new 40 Gigabit Ethernet technology — LX4 offered by Juniper. This transceiver module uses the same infrastructure as 10 GbE. The LX4 technology can meet all the performance criteria of today’s data center in which two multimode fiber strands and duplex LC connectors are used for 40GbE connectivity just like existing 10GbE infrastructure.

As the above mentioned, QSFP-40G-LX4 transceiver provides the ability to transmit full-duplex 40Gbps data traffic over one duplex multimode fiber cable with LC connectors. In other words, this transceiver delivers 40 Gbps over duplex OM3 or OM4. It can achieve the direct connection from 10 Gbps to 40 Gbps through LC duplex fiber cable. The QSFP-40G-LX4 has four 10Gbps channels. Each channel can transmit and receive simultaneously on four wavelengths over a multimode strand (see the following figure). Thus, the 40Gbps link can be connected by two multimode strands. QSFP-40G-LX4 connections can support the data transmission distance up to 100 meters over OM3 and 150 meters over OM4.

QSFP+ LX4 Saving Cost

When preparing to migrate from 10G to 40G network, cost is one of the most important thing to be considered. As we know, existing 10Gbps connections commonly use MMF cables with LC connectors. While most 40Gbps connections often need eight fiber strands, each four parallel strands for transmitting and receiving respectively. Take 40G-QSFP-SR4 an example, it uses 12-fiber MPO cable. Under that condition, 10Gbps cabling infrastructure should be upgraded to migrate to 40Gbps. It will cause additional cost of new patch cables, new patch panels, and expansion of the current fiber trunk.

However, QSFP LX4 transceiver can solve the cost issue. With QSFP-40G-LX4, it’s much easier to migrate from 10G to 40G network without considering the problem of deploying new cabling infrastructure or buying migration cassettes. Instead, it only needs to replace the 10GbE optical module with 40G-LX4. Because QSFP+ LX4 uses LC connectors. It allows the same cables to be used for direct 10 Gbps connections to direct 40 Gbps connections, resulting in zero-cost cabling migration. No additional spending on cabling will be required if QSFP+ LX4 transceivers are used for all 40 Gbps links. As a result, users realize 100 percent investment protection of their existing infrastructure and incur no additional cabling costs. This is a significant advantage when compared to the cost of reconstructing the cabling system using QSFP SR4 transceivers. If the cabling for this network is an expansion to the existing cabling system, the 40 Gbps connections can be built using MMF cables and QSFP SR4 transceivers or QSFP+ LX4 transceivers. QSFP+ LX4 can save a lot for 40 Gbps migration.

Conclusion

There are many solutions for the migration from 10G to 40G. QSFP+ LX4 technology
removes 40 Gbps cabling cost barriers for migrating from 10 to 40 Gbps in data center networks. QSFP+ LX4 transceivers provide 40 Gbps connectivity with huge cost savings and simplicity for next-generation data center 40GbE deployments. The QSFP+ LX4 transceiver allows organizations to migrate their existing 10 Gbps infrastructure to 40 Gbps at zero cost of fiber, and to expand the infrastructure with low capital investment. FS.COM provides JNP-QSFP-40G-LX4 transceivers with high quality and 100% compatibility. All of Fiberstore transceivers have gone through test-assured program before reaching customers. If you need any help, please contact us via sales@fs.com.

Originally published at www.fiber-optic-equipment.com

FS.COM 40G QSFP BiDi Transceiver Solution

25 Gigabit Ethernet emerges as the shinning star. It provides another solution (10G-25G-100G) migrating to 100 Gigabit Ethernet. But for those who just want to use 40G network instead of 25G at present, then they need to upgrade from 10G to 40G connections. As to the migration from 10G to 40G, this article will introduce a cost-effective solution – 40G quad small form-factor plugable (QSFP) bidirectional (BiDi) transceiver solution.

Traditional 40G Transceivers Solution

Fiber cabling infrastructure of 10G and 40G transceivers are different. 10GBASE-SR transceivers require multimode fiber (MMF) cable with LC connectors. While 40GBASE-SR4 or CSR4 transceivers connect with MMF ribbon cable with MPO/MTP connectors. It means that 40G connectivity can’t reuse the 10G network cabling infrastructure. That causes great cost.

Except the connector type, there is another concern. 10GBASE-SR transceivers require 2 fiber strands per 10G link, while 40GBASE-SR4 and CSR4 transceivers need 8-fiber strands (actually it’s 12 fiber strands.). That is because 40GBASE-SR4 and CSR4 transceivers use 4 parallel fiber pairs (8 fiber strands) and each pair at 10G for total 40G full duplex. In this case, 4 fiber strands are not used and wasted.

Figure1. 40GBASE-SR4 transceiver: 12-fiber strands, only 8-fiber strands used

As a result, the connector's change and the increased fiber density required for 40GBASE-SR4 transceivers need a significant cable plant upgrade. That makes it expensive for people to migrate form 10G to 40G network in their existing data centers.

40G QSFP BiDi Transceiver Solution

40GBASE-SR Bi-Directional QSFP is a short-reach transceiver that delivers 40 Gbps over a duplex OM3 or OM4 MMF connection. This connection can reach the distance up to 100 meters over OM3 MMF and 150 meters over OM4 MMF. This 40G transceiver has two 20G channels. Each channel transmits and receives two wavelengths over a single MMF strand. So the transceiver supports connections over a LC duplex MMF cable.

Figure2. 40GBASE BiDi transceiver: duplex LC

Cost Comparison

It may be not so intuitive that 40G QSFP BiDi transceiver solution can save more cost than the traditional 40G transceivers. Let’s take a look at the following case of upgrading 10G to 40G network and compare the cost of two kinds of solutions.

In an unstructured cabling system, devices are connected directly with fiber cables. This direct-attachment design is suitable for short distance connection in a data center.

Figure3. Direct 40G connections

From the figure, it shows that the 40G SR4 transceiver uses MPO connector and 40G QSFP BiDi transceiver uses LC connectors. Therefore, with 40G SR4 transceiver, to realize the migration, all of the existing 10G MMF cabling infrastructure should be replaced because the connector are different. But it’s another case to QSFP BiDi transceiver. The existing 10G MMF cables can be reused to achieve the network upgrade from 10G to 40G. This doesn’t require any cost on cables.

In the table, the cable costs and savings of migration and new deployment of 288 direct connections. To migrate the existing 288 10G to 40 connections, FS.COM QSFP BiDi transceiver doesn’t need any cost on cable. Compare to 40G SR4 transceiver, QSFP BiDi transceiver can save the cost by 100%.

Fiber Cable Lengths (meters)		10	30	50
288 connections for QSFP BiDi Transceiver	FS.COM LC MMF cables	2304	5760	9216
288 connections for 40G SR4 Transceiver	FS.COM MPO cables	21024	37440	51840
Cost Savings from 10G to 40G (US $)		21024	37440	51840
Cost Savings of New 40G deployment (US $)		18720	31680	42624

For the case in which 288 new direct 40G connections are needed in addition to the existing cabling infrastructure for a data center migration, the savings can reach as much as 82% with the use of QSFP BiDi transceiver. This above costs doesn’t include that of installation. It’s not hard to imagine the installation cost of 40G SR4 transceiver connections would be much higher.

Conclusion

QSFP BiDi transceiver is a new breakthrough in 40G network. It helps the users to realize the migration from 10G to 40G without the need of replacing all 10G cabling infrastructure. Actually, compared with solutions of some other companies, FS.COM 40G SR4 transceiver solution is already cheap. Since we devotes to serving our customers with the most cost-effective network connection solutions, we would like to introduce QSFP BiDi transceiver.

Originally published at www.fiber-optic-equipment.com