For 40GBASE-LR4 QSFP+ Transceiver Link: CWDM or PSM?

Nowadays, the 40 Gigabit Ethernet (GbE) system comes as the popular deployment among some enterprises for their high-performance fiber optic networks. And for 40GbE system, fiber optic transceivers are the indispensable high-capacity modules for multi-lane communications, like 40GBASE-LR4 QSFP+ transceiver. It’s known that 40GBASE-LR4 QSFP+ transceiver has two link options: coarse wavelength division multiplexing (CWDM) and parallel single-mode fiber (PSM). How much do you know about them? Can you figure out the differences between them? Following this article and you will get something.

40GBASE-LR4 CWDM QSFP+ Transceiver Brief

Compliant to 40GBASE-LR4 (eg. QSFP-40G-LR4) of the IEEE P802.3ba standard, this 40GBASE-LR4 CWDM QSFP+ transceiver uses a duplex LC connector as the the optical interface, able to support transmission distance up to 10km over single-mode fiber (SMF) used to minimize the optical dispersion in the long-haul system.

This kind of 40GBASE-LR4 QSFP+ transceiver converts 4 inputs channels of 10G electrical data to 4 CWDM optical signals by a driven 4-wavelength distributed feedback (DFB) laser array, and then multiplexes them into a single channel for 40G optical transmission, propagating out of the transmitter module from the SMF. Reversely, the receiver module accepts the 40G CWDM optical signals input, and demultiplexes it into 4 individual 10G channels with different wavelengths. The central wavelengths of the 4 CWDM channels are 1271, 1291, 1311 and 1331 nm as members of the CWDM wavelength grid defined in ITU-T G694.2. Each wavelength channel is collected by a discrete photo diode and output as electric data after being amplified by a transimpedance amplifier (TIA).

CWDM QSFP+, 2 optical SMFs with a duplex LC connector

40GBASE-LR4 PSM QSFP+ Transceiver Brief

Differently, PSM QSFP+ is a parallel single-mode optical transceiver and uses a MTP/MPO fiber ribbon connector instead of LC. Similarly, PSM QSFP+ also offers 4 independent transmit and receive channels, each capable of 10G operation for an aggregate data rate of 40G with 10km reach over SMF.

In a PSM QSFP+, the transmitter module accepts electrical input signals, while he receiver module converts parallel optical input signals via a photo detector array into parallel electrical output signals. Both the input signals and output signals are compatible with common mode logic (CML) levels.

PSM QSFP+, 8 optical SMFs with a MTP/MPO fiber ribbon connector


Allowing for the transceiver module structure, PSM seems more cost effective, since it uses a single uncooled CW laser which splits its output power into four integrated silicon modulators. Additionally, its array-fiber coupling to a MTP connector is relatively simple.

However, when taking the infrastructure into consideration, PSM would be more expensive when the link distance is long, because it uses 8 optical single-mode fibers while CWDM only uses 2 optical single-mode fibers. Besides, in the data center fiber infrastructure, the patch panel has to be changed to accommodate MTP cables, which would cost more than LC connectors and regular SMF cables. Besides, it’s a little difficult to clean MTP connectors. So CWDM is more ideal for 40GBASE-LR4 QSFP+ link.


For 40GBASE-LR4 QSFP+ transceiver link options, both CWDM QSFP+ and PSM QSFP+ support the maximum transmission distance of 10km. The former establishes 40G links over 2 optical SMFs with a duplex LC connector, and the latter achieves 40G links via 8 optical SMFs with a MTP/MPO fiber ribbon connector. Thus no change is required for migration from 10G infrastructure to 40G infrastructure, saving cost when CWDM QSFP+ is chosen. Fiberstore supplies a broad selection of 40GBASE-LR4 QSFP+ transceivers which are fully compatible with major brands, such as Finisar (FTL4C1QE1C). For more information about 40GBASE-LR4 QSFP+ transceivers, please visit Fiberstore.

Do You Still Worry About The Cost of Fiber Optic Transceivers?

transceiver moduleTo many users, there is an inevitable issue that the cost of fiber optic transceivers will keep adding up over time. This is why the demands of 3rd party compatible fiber optic transceivers have emerged in the market. Actually, 3rd party compatible fiber optic transceivers are the direct solution for a tight budgets. However, some issues mayoccur when using 3rd party compatible fiber optic transceiver that drive users to give it up. The worry of the cost of fiber optic transceivers still exists. This paper is going to talk about the fiber transceiver industry and discuss something you should know about the 3rd party compatible fiber optic transceivers.

Fiber Optic Transceiver Industry
When you buy transceivers for your switch, you are told to buy them from your network equipment manufacturer in order to keep your system running properly and safely. However, the switch vendor doesn’t actually manufacture these transceivers. In fact, the fiber interface transceiver manufacturers will supply a variant of their standard transceiver to the switch vendor for resale. The switch vendor will perform testing of that transceiver against their switch, create a compatibility matrix and SKU for that transceiver and start selling the transceiver. They mark up the price of the transceivers to cover their costs (to test/procure/stock etc..) and make a profit. This is why the “brand” transceiver modules are more expensive.

However, as long as the transceiver complies with the required IEEE and MSA standards all it would take is a quick compatibility test and for the vendor could publish a list of all supported transceivers. Thus, 3rd party compatible transceivers are not hard to be realized. In order to corner the market, the switch vendor will request that the transceiver vendor flash the transceivers EEPROM with a vendor specific identifier. The switch operating system will use the I2C bus to query the transceiver EEPROM data, and verify that the transceiver has the correct identifier. If the identifier doesn’t match, then the OS will not power up the laser. The idea is that the switch vendor doesn’t want you to put anything into your router which hasn’t been approved by them. This is why many users will face error warning when using the 3rd transceivers.

How To Solve? – “My 3rd party transceiver does not work on my switch”
So, how to solve this issue and successfully use 3rd party transceivers on your switch? First, you should know the hidden commands of your switch. I believe some of my blog fans may know it as I have explain it some weeks ago in another papers. Yes, the “service unsupported-transceiver” command. Certainly, it is take Cisco for example, but it is easy to find the equivalent commands in other brand switches along the way. (For more details can visit this paper link.)

3rd Party Transceivers vs “Brand” Transceivers
User who have experience of buying 3rd party transceivers and “brand” transceivers may know that the the major difference is cost. So, how much difference? Assuming you get an identical transceiver from Cisco and Fiberstore, the list price for an SR SFP+ transceiver from Cisco is $1,495 USD, while Fiberstore’s one just listed at $ 18.00 USD. This difference is incredible, but it is the truth. The truth is that you won’t have to sacrifice any quality or reliability with all of the savings you receive. In contrast, you get everything you’ve come to expect from the 3rd party transceivers at up to 90% off list price. As high-density merchant-silicon based switches become mainstream, the per-port cost of the switch is dropping dramatically. The transceiver costs now become a very large part of the total system cost and, for a 48-port switch the transceiver costs could easily exceed the base cost of the switch. 3rd party transceivers help users to save more on their cost of transceivers, so why not do it?

Of course, 3rd party transceivers are good option for your transceivers solutions. However, at least so far, the market is not fully normalized. Though the prices of 3rd party transceivers are very attractive, but the good and bad are intermingled. If you plan to buy the 3rd party transceivers for your switch, you had better to choose a vendor with high reputation. I recommend Fiberstore for you. Why? You may know the answer after you try.

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Digital Optical Video Fiber Optical Transceiver in Highway Monitoring System

Nowadays there are 3 grades in highway toll stations, toll station, sub-center and center. It seems a separation structure, but it is high efficient centralized management. All the charge stations are far away from monitoring center, and the monitor and control system need to upload images, so point to point fiber transceiver for image transmission is not an ideal, the highway toll station applied the multi-channel video image transmission in the form of transport nodes machine cascade that both N toll station through the video matrix switch out of 2 (or 3, 4) video images through video nodes by 1 core fiber optical transceiver cascade transmitted to the monitoring center. At the same time, the toll station monitoring (holder, lens, matrix switch, etc.) reverse control data transmission by the charging station to provide a data channel.

Highway video transmission system’s main purpose is to put the front end of the video signal and control signal transmission adopts optical transceiver system to road management center. For example, XFP and X2 module.

The section of monitor sub-center monitoring information on a particular road, video signals including road surface monitoring, the monitoring and controlling of the tunnel. Road surface monitoring mainly in entrances and exits, road crowded area and accident-prone area.Tunnel monitoring object is inside the tunnel and the driveway, portal, sidetracked and channel distribution.

And the character of the image inside the tunnel is very scattered and concentrated, Image is dispersion and concentration, perhaps only every a few hundreds of meters will come out tunnel road images, and a few kilometers of tunnels can be up to hundreds of images, each image distance between 120 meters to 150 meters or so.

Road surface monitoring image is more complexed. To fully monitor sections are at intervals of about 2 km image all the way, what the characteristic of this is more scattered.

Because these images will directly reflect each point on the road of actual traffic conditions, monitoring sections of sub-center was required to put forward the fiber optic transceiver system. Generally we should use digital real-time image compression, and optical transmission of optical transceiver become our first choice.

The application of digital video optical transceiver has improved the efficiency of the toll booths, convenient for different toll station business data transmission, and the centralized management of different data.

The world in the future is a digital world. On the way to the digital world, Digital video optical transceiver in the security industry is already very mature. There are more than one hundred optical terminal vendors in the world to provide optical transceivers. FS.COM is a professional optical transceivers company, provide high quality service. We avoid vicious competition, build and manage our own brand, providing customers with better products and services, let the light end factory can better development. For more information about us, please visit our website or contact with our customer service.

The Principle of Buying Fiber Optic Transceiver

In the actual purchase, the enterprise considered an important factor is the price, especially small and medium-sized enterprises and SOHO office. We believe that a few hundred dollars, sufficient to meet the general needs of enterprises, except for special industries, such as telecommunications, military. Of course, in addition to price, but also must consider the compatibility of the product with the surrounding environment in line with and the product itself, stability, reliability, otherwise the low price and then bought useless. In order to be able to pick a good fiber optic transceiver to purchase points listed below:

1. Take a look at itself whether to support full-duplex and half-duplex, because some chips on the market, only to use full-duplex environment, can not support half-duplex, if then switch to other brands (N-Way Switch) or HUB, using a half-duplex mode, will cause a serious colision and packet loos.

2. Take a look at the connection test whether it be done with other fiber optic connectors, fiber transceiver currently on the market is more and more, such as the mutual compatibility of different brands transceiver test did not do it in advance will also have packet loss, transmission time is too long, unsteadiness.

3. Take a look at whether it is to prevent the loos of safety devices, because many manufacturers in the production of fiber optic transceivers, in order to reduce costs, often using the data transfer mode register, the biggest drawback of this way, the data transfer will be unstable, resulting in the loss, and the best way is to use a buffer circuit design, safe to avoid data loss.

4. To see whether the product has to do temperature tests because fiber optic transceivers will produce high fever, coupled with its installation environment usually outdoors, so the temperature is too high (can not be greater than 50°C), fiber optic transceivers whether normal operation, the user is very important factor to consider! The maximum allowable working temperature is how much? Equipment for one to need long-term running this very worthy of our attention!

5. To see whether the product in accordance with IEEE802.3 standard? The fiber-optic transceivers, such as to comply with the IEEE802.3 standard, if you do not meet the standards, then certainly there is a compatibility problem.

6. Weigh the manufacturer’s service Imagine, if your equipment is broken, the factory a few days did not solve the problem, your loss is much ah? Therefore, in order to make the after-sales service timely early response, suggest that you select when the region with superb strong technical force, reputable professional company. Only rich experience in troubleshooting professional technical engineers, more advanced tools of detection failure!

7. The purchase carefully observe the appearance of the product, and the fiber module housing has old, whether shiny or has signs of wear. In today’s market, many vendors in order to reap huge profits, used in fiber optic transceiver, optical switches and other equipment used or old fiber module used fiber optic module, caused a great deal of hidden network transmission, such as: optical fiber the optical path of the module to be contaminated on the signal transmission must be affected by a decline in the quality of transmission. The transmission quality drops, on the reception sensitivity also cause reduced, can also cause data loss phenomenon. Plus the fiber module used in the service life will be compromised at any time parts failure.

Fiber Optic Transceiver Notes

Fiber optic transceivers have a variety of different classification, while most of the actual use note the distinction between the categories according to different fiber optic connectors: SC connector fiber optic transceivers and FC / ST connector fiber optic transceiver.

Connect different devices using fiber optic transceivers, must pay attention to the use of the port.

1. Fiber optic transceiver connection to 100BASE-TX devices (switches, hubs):

Verify that the maximum length of twisted pair does not exceed 100 meters;

To the fiber-optic transceiver connected to one end of the twisted pair RJ-45 port (Uplink port), the other end of the RJ-45 port 100BASE-TX set (switches, hubs) (general population).

2. Fiber optic transceiver connection to 100BASE-TX device (NIC):

Verify that the maximum length of twisted pair does not exceed 100 meters;

Connect one end of the twisted pair to fiber optic transceiver RJ-45 port (100BASE-TX port), and the other end to the RJ-45 port of the network card.

3. Fiber optic transceiver connected to 100BASE-FX:

Recognized that the fiber does not exceed the length of the distance range of the equipment can provide;

SC / ST connector 100BASE-FX fiber connect one end of the fiber optic transceivers SC / FC / ST connector, connect the other end equipment.

Also need to add a lot of users in the use of optical transceivers that: as long as the length of the optical fiber in the single-mode fiber or multimode fiber can support a maximum distance you can normally use. In fact, this is a wrong perception, this understanding is correct only when connected devices are full-duplex devices, when there are half-duplex devices, optical fiber transmission distance there is a certain limit.