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Difference Between 40G QSFP+ Transceiver with LC Interface and MTP/MPO Interface

Data transmission with higher density and bandwidth has become the trend under present networking environment. With 40 Gigabit Ethernet commonly deployed in most data centers, various network devices designed for 40 Gigabit Ethernet (GbE) link are available on the market. Among them, 40G QSFP+ transceivers play an important role in driving the bandwidth to a mounting point. There are mainly two interfaces adopted by 40G QSFP+ transceivers—MTP/MPO and LC. What is the difference between these two interface types? This article will have an analysis of the 40G QSFP+ transceivers with LC interface and 40G QSFP+ transceivers with MTP/MPO interface.

40G QSFP+ Transceivers With LC Interface

From the figure below, we can easily understand the working principle of 40G QSFP+ transceivers with LC interface. In the transmit side, 4 channels of 10G serial data streams at different wavelengths are passed to laser drivers. The laser drivers control directly modulated lasers (DML) with wavelengths. Then the output of the four DMLs are optically multiplexed to a SMF through an industry-standard LC connector, combining as 40G optical signal. In the receive side, the 40G optical signal is demultiplexed into four individual 10G optical data streams at different wavelength. And each wavelength light is collected by a discrete photo diode and amplified by a TIA, and then outputted as electric data. In this process, a 4-wavelength CWDM multiplexer and demultiplexer is used over a pair of single-mode fibers. For transmission distance of this type of 40G QSFP+ transceiver, take 40G LR4 QSFP+ transceiver as an example, it can support an optical link length up to 10 kilometers over the single mode fiber.

40G QSFP+ Transceivers With MTP/MPO Interface

We can easily understand the working principle of 40G QSFP+ transceiver with MTP/MPO interface from the figure below. In the transmit side, the transmitter converts parallel electrical input signals into parallel optical signals through the use of a laser array. Then the parallel optical signals are transmitted parallelly through the multimode fiber ribbon terminated with MPO/MTP fiber optic connector. In the receive side, the receiver converts parallel optical input signals via a photo detector array into parallel electrical output signals. Generally, 40G QSFP+ transceivers with MTP/MPO interface are utilized for short distance transmission over multimode fiber (MMF), like 40G SR4 QSFP+ transceiver, it can support a link length up to 100 meters on OM3 cable and 150 meters on OM4 cable.

Note: there are also some 40G QSFP+ transceivers with MTP/MPO interface supporting long distance transmission over SMF. For example, 40G LR4 PSM QSFP+ transceiver, a parallel single-mode optical transceiver with an MTP/MPO fiber ribbon connector, it offers four independent transmit and receive channels, each capable of 10G operation for an aggregate data rate of 40G over SMF. That is to say, eight single-mode fibers are used to achieve parallel transmission, with transmission distance up to 10 kilometers. From the perspective of cost, this kind of 40G QSFP+ transceivers cost more than 40G QSFP+ transceivers with LC interface. Besides, in the data center fiber infrastructure, MTP patch panel has to be used to accommodate MTP cables, which would cost more than LC connectors and regular SMF cables.

4x10G Connectivity

For the 40G QSFP+ transceivers with LC interface, they cannot be split into 4x10G as they use 4 wavelengths on a pair of single-mode fibers and do not lend themselves to “splitting” into 4 pairs without substantial complexity to split out the wavelengths. For the 40G QSFP+ transceivers with MTP/MPO interface, they can be used in 4x10G connectivity via an external 12-fiber parallel to 2-fiber duplex breakout cable, which connects the 40G module to four 10G optical interfaces.

Conclusion

Generally speaking, the 40G QSFP+ transceivers with LC interface are used for long distance transmission over single-mode fiber (SMF), and 40G QSFP+ transceivers with MTP/MPO interface are utilized for short distance transmission over multimode fiber (MMF). However, for some 40G QSFP+ transceivers with MTP/MPO interface, such as 40GBASE-LR4 PSM QSFP+ transceiver, it can support long distance transmission over SMF.

Whether to Use EDFA Amplifier in Long WDM System Or Not?

Currently, utilizing WDM technology to deploy the optical network has received widespread attentions, which enables higher capacity for data transmission. However, the technology is also limited by the transmission distance. When deploying a long WDM system, the signal power would still become weak due to the fiber loss. In order to address the issue, using EDFA amplifier to directly enhance the WDM signals would be a good choice for current and future optical network needs. The optical network combining WDM technology and EDFA module together can transmit multiple signals over the same fiber, at lengths up to a few hundred kilometers or even transoceanic distances. To better know how does EDFA amplifier work in the long WDM system, let’s learn the EDFA amplifier knowledge and analyze the performance of WDM system bonding with the EDFA module.

Introduction to EDFA Amplifier

EDFA amplifier, also referred to as erbium-doped fiber amplifier, is basically composed of a length of Erbium-doped fiber (EDF), a pump laser, and a WDM combiner. When it works, the pump laser with 980 nm or 1480 nm and the input signal around 1550 nm can be combined by the WDM combiner, then transmitted and multiplexed into the Erbium-doped fiber for signal amplification. The pump energy can be transmitted in the same direction as the signal (forward pumping), or the opposite direction to the signal (backward pumping), or both direction together. And the pump laser can also using 980 nm or 1480 nm, or both. Taking the cost, reliability and power consumption into account, the forward pumping configuration with 980nm pump laser EDFA amplifier is always the first choice to enhance the signals for a long WDM system.

Analysis of WDM Network Without EDFA Amplifier

Before analyzing WDM network deployed with EDFA amplifier, it is necessary to know the basic configuration of an original WDM network, as shown in the figure below. We can learn that four signals from different channels are combined by the optical combiner. And then, the integrated signals are transmitted through an optical fiber. Thirdly, the signals are split into two parts by the splitter. One part passes through the optical spectrum analyzer for analyzing signals, and the other one goes through the photo detector to be converted into electrical signal and then be observed by the electrical filter and scope. However, in the process, the signal power gets highly attenuated after being transmitting at long distance.

Analysis of WDM Network Using EDFA Amplifier

By using the EDFA amplifier, we can easily overcome the attenuation of long WDM network. From the following figure, we can learn that EDFA amplifiers act as booster amplifier and pre-amplifier to enhance the signal, so that system will no longer suffer from losses or attenuation. Therefore, if you need to deploy a long WDM system, it is highly recommended to deploy the EDFA amplifiers in the system that features flat gain over a large dynamic gain range, low noise, high saturation output power and stable operation with excellent transient suppression. It is an undoubtedly ideal solution with reliable performance and relatively low cost to extend the WDM network transmission distance.

Conclusion

It is well know that the signal power would be greatly attenuated when the transmission distance is long enough. Hence, when deploying a long WDM network, it is definitely necessary to use the EDFA amplifier to enhance the signal strength, allowing for the long transmission distance. As a preferable option, the EDFA amplifier with very low noise is relatively insensitive to signal polarization and easy to realize signal amplification.

Brief introduction for 40G QSFP+ SR4 Transceiver

As 40G network has been widely applied in today’s data center cabling system, 40G QSFP+ transceivers gain great popularity among data center managers. And for short data transmission distance, 40G QSFP+ SR4 transceiver is preferred. This article is going to focus on 40G QSFP+ SR4 transceiver and share several cabling solutions for 40G QSFP+ SR4 with you.

Overview of 40G QSFP+ SR4 Transceiver

40G QSFP+ SR4 transceiver is a parallel fiber optic transceiver which means it uses four fibers for transmitting and four fibers for receiving at the same time. Designed with MTP/MPO interface, 40G QSFP+ SR4 transceiver is used together with multimode fiber, such as OM3 and OM4. Working on wavelength of 850 nm, 40G QSFP+ SR4 transceiver can support 40G fiber optic transmission with the link length up to 100 meters over OM3 fiber and 150 meters over OM4 fiber. For application, 40G QSFP+ SR4 transceiver can be used for 10G to 40G and 40G to 40G connections. Here is a figure of 40G QSFP+ SR4 transceiver for you.

10G to 40G Connection

Since 40G QSFP+ SR4 transceiver uses four independent full-duplex transmit and receiver channels, the 40G optical signal can be split into four 10G optic signals. Therefore, we can increase the fiber count at the 10G distribution end to realize 10G to 40G connection. As the following figure shows, we can use 12f MPO trunk cable and fiber enclosure. Four 10G SFP+ SR transceivers are inserted into 10G ports on one side, while one 40G QSFP+ SR4 transceiver is inserted into 40G port on the other side. Then the four 10G SFP+ SR transceivers are connected with four duplex LC patch cables which are plugged into LC ports on the front side of MPO fiber cassette inside the fiber enclosure, and the 40G QSFP+ SR4 transceiver is connected with 12f MPO trunk cable which is plugged into MTP/MPO port on the rear of MPO fiber cassette. Finally, the whole optical link is completed.

We can also use MPO to LC fanout and MTP fiber patch enclosure which includes MTP fiber adapter panels. This cabling solution is similar to the previous one, but the difference is that the four 10G SFP+ SR transceivers are connected with MPO to LC fanout which is plugged into MTP/MPO port on the MTP fiber patch enclosure. The scenario is shown in the following figure.

40G to 40G Connection

The following figure shows the simplest scenario for 40G to 40G connection. Two 40G QSFP+ SR4 transceivers are separately inserted into two 40G switches. Then the two 40G QSFP+ SR4 transceivers are connected by 12f MPO trunk cable.

We can also use MTP fiber patch enclosure to achieve better cable management and higher density cabling. The scenario is shown in the following figure. With the use of MTP fiber enclosure, cable management for 40G to 40G connection could be easier. A 48-port 1U rack mount MTP fiber patch enclosure includes up to four 12-port MTP fiber adapter panels with MPO MTP fiber optical adapters on it, here is a figure for you.

Conclusion

Designed with parallel transmission mode, 40G QSFP+ SR4 transceiver has a wide range of cabling applications with great flexibility. The cabling solutions mentioned above are just several commonly used ones. As for detailed cabling solutions for 40QSFP+ SR4 transceiver, it is suggested to depend on the practical applications and cabling environments. I hope after reading this article, you can learn more about 40G QSFP+ SR4 transceiver.

Three Cabling Solutions for 40G Network

Network technology has been developed rapidly and many data centers are utilizing 40G network to satisfy their needs for high density cabling and high speed data transmission. When it comes to 40G network cabling solutions, MPO fiber optic cable assemblies are most used by data center managers. This article is going to introduce three cabling solutions for 40G network—cabling with no conversion component, cabling with conversion module and cabling with conversion harness.

Cabling With No Conversion Component

For cabling with no conversion component solution, in fact, it is a Base-12 MTP connectivity solution. The 12-fiber MTP trunk cables are deployed in the whole 40G connectivity. But in this cabling solution, four fibers are not used. Apart from this, there will be additional cost associated with the purchase of additional fibers. Though this solution does notuse 33% of the installed fiber and may require more cable raceway congestion, it does have the advantage of simplicity and lowest link attenuation.

Cabling With Conversion Module

With the use of conversion module MPO patch panel, the unused fibers can be converted into usable fiber links. For every two 12-fiber MTP connectors in the backbone cable, we can create three 8-fiber links. Using Base-12 connectivity and Base-8 connectivity together realizes 100% fiber utilization. When reusing existing deployed MTP cabling, great value will be gained if using conversion module to use all previously deployed fibers, and we can eliminate the cost of having to deploy additional cabling.

Cabling With Conversion Harness

The cabling with conversion harness solution uses standard MPO patch panel and 2×3 MPO conversion harness. It can achieve full fiber utilization. Although it seems attractive, it involves considerable cabling challenges. For instance, if you only need two 40G connections to the equipment, what do you do with the third 8-fiber MTP connection? Or what if the 40G ports are in different chassis blades or completely different chassis switches? The result will be long assemblies, which will be difficult to manage in an organized way. For this reason, this kind of solution is expected to be the least desirable and so the least deployed method.

Which One to Choose?

If you are installing new cabling, then you can consider cabling with no conversion component solution, assuming that the cable raceway is not a concern. If you are using previously installed MTP trunks, cabling with conversion module solution is recommended which can realize 100% fiber utilization while maintaining any port to any port patching. The cabling with conversion harness solution is typically deployed only in specific applications, such as at the ToR switch, where 40G ports are in a close cluster and patching between blades in a chassis switch is not required.

Conclusion

It is not difficult to find that each type of cabling solution has their own advantages and disadvantages. As for which on to choose, it all depends on your specific network deployment environment and requirements. After reading the content above, I hope you can have a better understanding of these three cabling solutions for 40G network and choose a suitable cabling solution for your network deployment.

Things Should Be Noticed Before Choosing 24-Fiber MPO Cable

In the process of migrating to greater bandwidth 40G and 100G network, MTP cabling system which provides high density and high performance plays an important role. Whether to use 12-fiber or 24-fiber MPO cable has been a hot topic in higher speed networking migration. In my previous blog Choosing 24-Fiber MPO/MTP Cabling for 40/100G Migration, we have indicated that MPO 24 fiber cable is more suitable for 40G and 100G network. Besides, with active equipment planning to use a single 24-fiber MPO interface for 100G and the channel currently requiring 20 fibers, many IT managers are also considering the use of 24-fiber MPO solutions. However, before choosing 24-fiber MPO cable, there are some facts that should be noticed.

The Higher the Fiber Count, the Higher the Loss

Optical loss budget is a big concern among data center managers, and due to limitations in the protocol, standards now require a total connector loss budget of 1.0 dB for 40G and 100G, but a 24-fiber MPO connector typically has a loss of 0.5dB which is much higher than 0.2dB that 12-fiber MPO connector has. This is mainly due to the fact that the more the fiber count, the higher the loss. The higher loss of the 24-fiber MPO limits data center managers to having just two mated pairs in a channel.

Note: Current proper polishing technique can address 24-fiber MPO to meet the low loss requirement as 12 fiber MPO connector. For example, 24-fiber MTP trunk cable in fiber-mart.COM only has 0.35dB insertion loss.

The Higher the Fiber Count, the More Difficult to Control End-Face Geometry

In a quality fiber connector, the fibers protrude slightly beyond the ferrule. When two fibers are mated using the right pressure, the fibers will deform slightly to fill in any gaps and provide a solid mating. Any variance in the pressure can impact the insertion loss and return loss on a fiber-to-fiber basis. To achieve consistence pressure, it is important to have a very flat ferrule after polishing with all the fibers protruding equally. With higher count arrays, like 24-fiber MPOs, there are more fibers to control, which can significantly increase the odds for height variance. For example, in the following 72-fiber array, if we look at this graphic of the middle two rows of fibers, we can see the variance in the height profile. The height variance becomes even more pronounced across more rows of fibers. Besides, it is more difficult to achieve a flat ferrule polishing on a large array area.

Although the polishing technique has been significantly improved, there still exists limitation to achieve a flat end-face and equal pressure over the array.

Standards and Testing Remain an Issue to 24-fiber MPO Cabling

100GBase-SR4 standard has be a reality and that most of users is running 100G over 8 fibers, rather than 20, which will render the 24-fiber MPO a dated interface for 100G Ethernet. In addition, the MPO cabling testing is far more complicated than duplex cabling testing. You have to gain very professional training, tools understanding that you can efficiently conduct multifiber testing. In other words, if there is any issue with the multifiber cabling, it’s not easy to troubleshoot it.

It’s Still Your Choice

With the significant demand for higher speed 40GbE and 100GbE, MPO cabling has become more popular than ever. We have indicated that 24-fiber MPO cable reveals more advantages than 12-fiber MPO cable, however, before choosing it, there are more factors we have talked above that should be taken into consideration.

100G Single-Mode Modules for Short Distance Transmission

As bandwidth demand continues to grow, network service providers are looking at 100G Ethernet network to accommodate the constant traffic surge. This new technology translates into greater speeds and a possible network infrastructure upgrade to compensate for various challenges that do not apply to slower networks, such as 10G, or 40G. 100G Ethernet provides high-speed connectivity while protecting current network infrastructures that requires broad expertise and wide-range testing to qualify the state of the fiber, perform fiber characterization and assess the integrity of data transmission over long-haul and ultra-long-haul networks. In response to 100 Gigabit Ethernet, many famous telecommunication companies, like Cisco, have delivered industry-leading, standards-compliant, 100G pluggable transceiver modules, such as single-mode QSFP-100G-LR4 for the transmission distance up to 10 km and multimode QSFP-100G-SR4 for the transmission up to 100 m. How about single-mode 100G modules for the transmission distance less than 2 km? Today, we’re going to introduce two 100G interfaces over single-mode fiber for short distance transmission: 100GBase CWDM4 and 100GBase PSM4.

The Development History of 100GBase CWDM4 and 100GBase PSM4

The IEEE standardized a cost-effective 100m solution known as “SR4”. Beyond 100m, there is only the “LR4” standard, which is targeted to achieve 10km. Customers, particularly hyperscale data centers are looking for solutions up to 2 km. To response, in 2014, a new industry group CWDM4(coarse wavelength division multiplexed 4x25G multi-source agreement) MSA which is consisted of Avago Technologies, Finisar Corp, JDSU, Oclaro, and Sumitomo Electric, announced the formation of an industry consortisum dedicated to defining specifications and promoting adoption of interoperable 2km 100 interfaces over duplex single-mode fiber, which smooths the process of getting to 100Gb Ethernet.

Like the development history of 100GBase-CWDM4, in order to fill the requirement of low-cost 100G connections at reaches of 500 m in applications that fall in between the IEEE standardized multi-wavelength 10-km 100GBase-LR4 single-mode approach and its multimode-fiber based 100GBase-SR10 short reach specification, six technology vendors aim to promote the creation and adoption of parallel single-mode 4-lane (PSM4) approach to 100G in the data center.

Main Features of 100GBase-CWDM4 and 100GBase-PSM4

100GBase-CWDM4: 100GBase CWDM4 module comply with the requirement of CWDM4 MSA. It is a 100G optical module using CWDM (coarse wavelength division multiplexing) technology with 4 lanes of 25Gbps optically multiplexed onto demultiplexed from a standard duplex G.652 single-mode LC or SC fiber for the link length from 2 meters to at least 2 kilometers. Transceiver modules compliant to CWDM4 MSA specification use a color code to indicate the application. The color code can be on a module bail latch, pull lab, or other visible feature of the module when installed in a system The image below shows the working principle of 100GBase-CWDM4.

100GBase-PSM4: 100GBase-PSM4 is a parallel module which provides increased port density, offering four independent transmit and receive channels, and each channel operates at 25Gbps, resulting in an aggregate data rate of 100Gbps for optical communication applications. It can support the link length up to 500 m over single-mode MPO or MTP fiber. The working principle of 100GBase-PSM4 is shown below.

Which One Is More Cost Effective?

From an optical transceiver module structure viewpoint, PSM4 can be more cost effective, this comes in two reasons: One is that it uses a single uncooled CW laser which splits its output power into four integrated silicon modulators, the other is that its array-fiber coupling to an MTP connectors is relatively simple.

However, from an infrastructure viewpoint, PSM4 would be more expensive when the link distance is long, mainly due to the fact that PSM4 uses 8 optical single-mode fibers, while CWDM4 uses only 2 optical single-mode fibers.

When take these two factors into considerations, a total cost comparison can be qualitatively shown in the figure below. As can be seen in the figure, PSM4 starts with a lower cost due to its lower transceiver cost, but as the link distance increases, its total cost climbs up very fast due to the fact that it uses 8 optical fibers. Besides, if deploying PSM4 modules, the entire optical fiber infrastructure within a data center, including patch panels, has to be changed to accommodate MTP connectors and regular single-mode fiber cables. In addition, cleaning MTP connector is not a straightforward task.

Conclusion

With the requirement for longer distances and higher data transmission speed increases, 100GBase-CWDM4 and 100GBase PSM4 which provide lower-cost, lower power option for what can be referred to as medium-reach distances that is future-proof for the next generations of data transmission speeds. fiber-mart.COM offers compatible 100GBase-CWDM4 and 100GBase-PSM4 for many brands at affordable price. You can choose the right one according to your need.