Check out All CWDM Transceiver Modules

Coarse Wavelength Division Multiplexing (CWDM) is one of WDM technologies. It uses up to 20 different wavelengths for data transmission over a single fiber. CWDM applies coarse wavelength grid and it allows low-cost, uncooled lasers, which makes CWDM systems less expensive and consuming less power. There are many optical equipment applying CWDM technology. This article will introduce CWDM optical transceivers.


CWDM Transceivers

CWDM transceiver is a kind of optical modules employing CWDM technology. CWDM transceivers enable connectivity between existing network equipment and CWDM Multiplexers/DeMultiplexers (Mux/DeMux). When used with CWDM Mux/DeMux, CWDM transceivers can increase network capacity by transmitting multiple data channels with separate optical wavelengths (1270 nm to 1610 nm) over the same single fiber. CWDM transceivers are also useful for reducing network equipment inventories by eliminating the need to maintain surplus units/ devices of various fiber types for network repairs or upgrades. CWDM transceivers include four types, such as CWDM SFP, CWDM SFP+, CWDM XFP and CWDM X2. The following shows more details about these CWDM transceiver modules.

CWDM Transceiver Module Types

CWDM SFPs are hot-pluggable transceiver modules. CWDM SFP transceivers are SFP MSA (Multi Sourcing Agreement) and IEEE 802.3 & ROHS compliant. CWDM SFPs can provide data rates including 1G, 2G and 4G over the link distance of up to 200 km by connecting with duplex LC single-mode patch cords. CWDM SFPs transmit multiple data channels by combining separate optical wavelengths onto a single fiber to increase network capacity. CWDM SFPs can be used to support the CWDM passive optical system combing CWDM OADM (optical add/drop multiplexer). When CWDM SFPs used with transponders and media converters, these two optical components offer convenient method to convert existing legacy equipment with standard wavelengths or copper ports to CWDM wavelengths.


CWDM SFP+ offers service providers and enterprise companies an easy way to get a scalable 10 Gigabit Ethernet network. It is a cost-effective solution for 10 Gigabit Ethernet applications in campus, data center and metropolitan area access networks. CWDM SFP+ can transport up to eight channels of 10 Gigabit Ethernet over single-mode fiber strands at the wavelengths including 1610 nm, 1590 nm, 1570 nm, 1550 nm, 1530 nm, 1510 nm, 1490 nm, and 1470 nm. CWDM SFP+ solution is helpful to increase the bandwidth of an existing 10 Gigabit Ethernet optical infrastructure without adding new fiber strands. The solution can be used in parallel with other SFP+ devices on the same platform.


CWDM XFP is a hot-pluggable module designed in Z-direction and mainly used for typical routers and switch line card applications. CWDM XFP transceivers are designed for Storage, IP network and LAN. They comply with CWDM XFP MSA. CWDM XFPs cover the wavelengths from 1270 nm to 1610 nm. These modules can support the distance up to 100 km, which depends on the wavelengths, fiber types and the CWDM Mux/DeMux insertion loss.


CWDM X2 transceiver is designed for CWDM optical data communications such as 10G Ethernet and 10G Fibre Channel applications. CWDM X2 wavelengths are available from 1270 nm to 1610 nm. CWDM X2 is MSA Compliant. It supports the transmission distance up to 80 km connecting with duplex SC single-mode fiber cable.


CWDM technology provides a low-cost solution which allows scalable and easy-to-deploy Gigabit Ethernet and Fibre Channel services. CWDM transceivers enable a more flexible and highly available multi-service network with the combinations of CWDM OADMs and CWDM Mux/DeMux. We offer all kinds of CWDM transceivers like CWDM SFP, CWDM SFP+, CWDM XFP, CWDM X2. Our CWDM transceivers are compatible with most famous brands and all these optics have been fully tested to make sure high compatibility. For more details our CWDM transceivers and other CWDM equipment, please visit our site or contact us via

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What’s the Difference Between Cisco GLC-SX-MM and Cisco GLC-SX-MMD?

Cisco 1000BASE SFPs keep a huge market share in the optic area. Cisco SFPs offer users optical solutions for long distance and short distance transmission. For short distance, there are 1000BASE SX SFP, such as Cisco GLC-SX-MM and Cisco GLC-SX-MMD. Though these two modules have great similarity, they are actually different. Then what’s the difference? This article will introduce details of Cisco GLC-SX-MM and Cisco GLC-SX-MMD SFP transceiver modules.


Cisco GLC-SX-MM 1000BASE-SX SFP is a duplex transceiver for short distance transmission, operating at the wavelength of 850 nm at the data rate of 1Gbps. It connects with OM2 multimode LC patch cords supporting up to 550 meters. The hot-swappable 1000BASE-SX SFP is compatible with the IEEE 802.3z 1000BASE-SX standard. And it’s RoHS compliant.


Cisco GLC-SX-MMD 1000BASE-SX SFP is another type of hot-swappable transceiver for short reach data transmission. This 1000Base-SX transceiver supports data rates up to 1.25Gbps. Same to Cisco GLC-SX-MM SFP, it also has duplex LC interference. Connecting with OM2 MMF, it can support the distance up to 550 meters. It’s compliant with SFP Multi-Source Agreement (MSA) standards. Cisco GLC-SX-MMD is composed of five parts: the LD driver, the limiting amplifier, the digital diagnostic monitor, the VCSEL laser and the PIN photo-detector. The Digital Diagnostic Monitoring (DDM) function is its special feature.

What Is DDM?

From the above content, you can see the main difference of these two transceivers is the DDM. When you buy SFP transceivers in the market, you may come across this selection difficulty whether to choose an SFP with DDM or not. So what’s DDM?

DDM is short for digital diagnostic monitoring. It’s also known as diagnostic optical monitoring (DOM). Diagnostic monitoring interface outlined in the SFF-8472 MSA is an extension of the serial ID interface defined in the GBIC specification, as well as in the SFP MSA. Today, many SFP transceivers have the function of digital diagnostics monitoring according to the industry standard MSA SFF-8472. It provides the important information about the status of the transmitted and received signals. This approach allows for better fault isolation and error detection.

DDM mainly plays the role in two sides: monitoring and warning. It monitors detailed information about a transceiver. And it offers a system of alarm and warning flags which alert the host system when particular operating parameters are not in line with the normal operating parameters set by the factory. So users can find out the fault isolation according to outcomes of DDM, and predict failure possibilities and prevent such fault.

Real-time monitoring—With a 2-wire serial bus (also known as “I2C” or “I2C” protocol), digital diagnostics can monitor the SFP module’s temperature, receiver power, transmitter bias current, and transmitter power by a microcontroller inside the transceiver. Usually, the output of the physical value of each parameter is an analog voltage or current from the Trans impedance amplifier, the laser driver, or the post amplifier. Then the digitalized value can be processed as part of a control loop, trigger an alarm, or just record the data into a register.

Calibration and warning thresholds—In addition to generating digital readings of internal analog values, DDM can also produce various status bits. Calibration and warning thresholds value is made during the device manufacturing process. Comparing current values generated by DDM and factory preset limits, users will know whether or not the transceivers have met the desired operation requirements.

FS.COM Cisco Compatible 1000BASE-SX SFP Solutions

FS.COM brings Cisco compatible 1000BASE-SX SFPs including GLC-SX-MM and GLC-SX-MMD SFPs.
The 1000BASE-SX standard optics are developed to support lower cost multi-mode fiber runs in horizontal and shorter-length backbone applications. The following figure shows two Cisco GLC-SX-MM SFP transceivers are connected by an LC MMF patch cable.


Item Part No. Description
a. 11774 Cisco GLC-SX-MM Compatible 1000BASE-SX SFP 850nm 550m Transceiver
b. 43132 2M LC UPC to LC UPC Duplex 2.0mm PVC(OFNR) OM2 Fiber Optic Patch Cable
b. 11774 Cisco GLC-SX-MM Compatible 1000BASE-SX SFP 850nm 550m Transceiver

Note: you can use GLC-SX-MMD SFPs to replace GLC-SX-MM SFPs for shorter-length backbone application, too.


This article introduces Cisco GLC-SX-MM and Cisco GLC-SX-MMD SFP transceivers. Both kinds can realize short distance connection. The difference is that GLC-SX-MMD has DDM function while the other has no. So it’s up to you to decide whether you need DDM function to monitor parameters of the SFP. Fiberstore supplies optical transceivers with DDM and without DDM to satisfy customers’ different needs. If you need more information, please contact us  or visit our site.

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How to Choose Satisfying SFP Transceiver Modules?

Today, various types of 1000BASE SFP transceiver modules can be found in the market. But should you choose one for long distance and short distance application? Or buy copper optics? Which brand is the most reliable and cost-effective, Cisco, Finisar, HP, etc.? Do the third-party optics operate as well? So how to find satisfying SFP transceiver modules which suit your switch most? Now keep reading this article and you will get the method. Take three most common types of Cisco SFP modules as example.

Three Types of Cisco SFP Modules

This GLC-SX-MM 1000BASE-SX SFP transceiver module is a duplex SFP transceiver for optical communications. It can support the data rate of 1Gbps reaching the distance up to 550 meters over OM2 multimode cable. The GLC-SX-MM transceiver operates at 850nm wavelength. It’s compatible with the IEEE 802.3z 1000BASE-SX standard, which is usually applied in Gigabit Ethernet. There are also GLC-SX-MMD and GLC-SX-MM-RGD SFP modules. “D” of GLC-SX-MMD means Digital Optical Monitoring (DOM) support which supports transceiver monitoring and troubleshooting operations. “RGD” of GLC-SX-MM-RGD refers to rugged (RGD) transceiver module, which features enhanced ESD (electrostatic discharge) protection, and extended operating temperature range.



The Cisco GLC-LH-SM 1000BASE-LX/LH transceiver is an LC duplex SFP transceiver applied for Gigabit Ethernet network. This module is designed for both short distance and long distance data transmission. If connecting with single-mode fiber patch cable, it can reach up to 10 km. If connecting with multimode fiber patch cable, it can go up to 550 meters. The GLC-LH-SM transceiver operates at 1310nm wavelength. This transceiver is compliant with Multi-Source Agreement (MSA) standards. LX means long wavelengths and LH is short for long haul. 1000BASE-LX is the Gigabit Ethernet standard specified to work over a distance of 5 km over single-mode fiber cable. 1000BASE-LH and 1000BASE-LH/LX are often used by the manufacturers. Thus, we often see 1000BASE-LX/LH instead of


The GLC-T 1000BASE-T SFP is a hot-swappable input/output device that plugs into a Gigabit Ethernet port or slot, linking the port with the network. It supports the max data rate of 1000Mbps reaching 100 meters links over copper cables such as Cat5, Cat5e or Cat6a. This transceiver is fully compliant with the MSA and 1000BASE-T standards as specified in IEEE 802.3-2002 and IEEE 802.3ab.


Original or Third-party?

“Third-party” means a supplier (or service provider) who is not directly controlled by either the seller (first party) or the customer/buyer (second party) in a business transaction. For fiber optics industry, all fiber optic transceivers are defined by Multi-Source Agreement (MSA). MSAs strictly define the operating characteristics of fiber optic networking equipment. Therefore, as long as a manufacturer complies to MSA guidelines, their transceiver modules will function and operate identically to other manufacturer’s MSA-compliant transceivers. For example, the above fiber optics like GLC-SX-MM, GLC-LH-SM and GLC-T made by FS.COM are completely compatible with Cisco networking equipment.

Whether to buy original or compatible SFPs may depend on the the cost. Original SFPs are much more expensive than the third-party modules. Using the third-party optics can absolutely help you save the cost. Considering the third-party SFPs from the third vendor, you may worry about the quality and compatibility. As to Cisco compatible GLC-SX-MM, GLC-T, GLC-LH-SM SFP modules, lots of vendors can produce these optics. So it’s necessary to ask information about OEMs and compatibility test from your third-party optics supplier.


From the above introduction, you must have a well understanding about three common Cisco 1000BASE SFPs. When choosing SFP modules, you should consider whether it matches the switch port and the cable you have prepared. If you have multimode cable, then you can choose GLC-SX-MM 1000BASE SFP. If you use single-mode fiber cable, you should select GLC-LH-SM 1000BASE SFP. While if your cable is copper category, you have to use GLC-T 1000BASE-T SFP. On condition that your budget doesn’t allow you to buy original brand module, you can buy the third-party optics from us with Cisco, Finisar, HP and other compatible brands. All the optics have gone through test for 100% compatibility. Any question, please contact us.

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How Much Do You Know About SONET/SDH SFP+?

Before, Plesiochronous Digital Hierarchy (PDH) system was used to transport phone calls and data over the same fiber. Since phone calls and data traffic increase a lot, SONET/SDH are introduced to replace PDH system to transport the data without synchronization problems. As you can see, you always find SONET/SDH SFP+ in the market. Now, this article will give a brief analysis on SONET/SDH SFP+.


SONET/SDH Interfaces Overview

SONET (Synchronous Optical Networking) and SDH (Synchronous Digital Hierarchy) are multiplexing protocols that transfer multiple digital bit streams over optical fiber with lasers or light-emitting diodes (LEDs). SONET and SDH are widely used methods today for very high speed transmission of voice and data signals across the numerous world-wide fiber-optic networks. SONET is the standard used in the United States and Canada, and SDH in the rest of the world. The two are largely equivalent. Although the SONET standards were developed before SDH, it is considered a variation of SDH because of SDH’s greater worldwide market penetration.

We often find SONET/SDH SFP transceiver like Cisco OC-3/STM-1 LR-1 SFP 1310nm 40km IND DOM. What does OC-3/STM-1 mean? OC-3c (Synchronous Transport Signal 3, concatenated) is the basic unit of SONET. Depending on the system, OC-3 is also known as STS-3 (when the signal is carried electrically). STM-1 (Synchronous Transport Module, level 1) is the basic unit of framing in SDH, which operates 155.52 Mbit/s. OC-3c and STM-1 have the same high-level functionality, frame size, and bit-rate.

SONET/SDH Data Rates
SONET/SDH and 10 Gigabit Ethernet

10 Gigabit Ethernet (10GbE) means the Ethernet network runs at 10 Gigabit per second. The 10 Gigabit Ethernet defines two PHY (Physical Layer) types: a local area variant (LAN PHY) with a line rate of 10.3125 Gbit/s, and a wide area variant (WAN PHY) with the same line rate as OC-192/STM-64 (9,953,280 Kbit/s).

10GbE provided the potential for an Ethernet solution aligned with the data rate of OC-192 backbone. It’s the first time in Ethernet history that no additional speed matching equipment would be required to link with the WAN. A seamless end-to-end Ethernet network can be built with less money. But the question is how to balance the compatibility with the installed base of OC-192 equipment while still meeting the economic feasibility criteria of the P802.3ae Task Force in defining the 10GE WAN PHY. To solve this problem, an OC-192 frame format is provided to support only the SONET overhead features required for fault isolation. This simplification avoids unnecessary functions and cost.

In order to make sure that WAN PHY optics would benefit from the high volumes and low cost of Ethernet, the serial 1310 nm and 1550 nm transceiver modules were kept the same as the LAN PHY. Since the 1310 nm and 1550 nm transceiver modules are designed for up to 10km and 40 km links respectively, they will inter-operate with OC-192 transceiver modules for 1310 nm and 1550 nm over intermediate reach, respectively.


We offers OC-192/STM-64 SFP+ for short reach (SR-1, VSR) , intermediate reach (IR-2) and long reach (LR-2) applications (as shown in the following table). These SFP+ modules are compatible with the SONET/SDH and ATM standards.


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Quick Guides on 3G Digital Video SFPs

As high definition (HD) content occupies the norm in video and broadcasting industry, higher standards digital video SFPs are needed for HD or even higher standard video transmission. So there are 3G digital video SFPs suitable for SD/HD/3G-SDI. To know more about 3G digital video SFPs, please continue to read this article.

SDI Standards

SDI, short for Serial Digital Interface, is a digital video interface standard made by SMPTE (The Society of Motion Picture and Television Engineers) organization. The serial interface transmits the data through single channel. Additional SDI standards include HD-SDI, 3G-SDI, 6G-SDI, and 12G-SDI. HD-SDI was standardized by SMPTE 372M in 1998. It can support 1.485Gbps interface. 3G-SDI consists of a single 2.970Gbps serial link that allows replacing dual link HD-SDI.

3G Digital Video SFPs

3G Video SFP is also named Digital Video SFP. Digital video SFP modules are specially applied for SDI (Serial Digital Interface) data rates from 50 Mbps to 3 Gbps with links of 80 km over single-mode fiber. This kind of SFPs are designed to transmit optical serial digital signals as defined in SMPTE 297-2006, specifically for robust performance in the presence of SDI pathological patterns for SMPTE 259M, SMPTE 344M, SMPTE 292M and SMPTE 424M serial rates.

Digital video SFPs are hot pluggable, easy to use, and offer the highest density optical solution for carrying digital video through optical fiber. The digital video SFP pinout is designed as one slot can be populated with a dual transmitter, dual receiver, single transmitter, single receiver, or a transceiver. Digital video SFP is a cost-effective way to solve the problems during digital video optical transmission, allow the transport of SDI and HD-SDI video signals over any optical transport system that employs MSA standard optical transceivers.

3G Digital Video SFPs Types

3G digital video SFPs include 3G SDI SFP, BiDi SFP and CWDM SFP. According to different standards, it can be divided into different types. Based on the transmission mode, it can be divided into single Tx, single Rx, dual Tx, dual Rx and TR transceivers; by standards into MSA and non-MSA; by operating wavelength into 1310nm, 1490nm, 1550nm and CWDM wave length. 3G digital video SFPs also have 3G video SFP and 3G video pathological patterns due to different applications. Let’s take a look at the details about 3G video pathological patterns SFP.

What are 3G-SDI pathological patterns? Pathological patterns, also called SDI proving ground, are a whole test signal. And it must be done during blackout. This signal is tough to handle by serial digital system, and significant to check the system performance. Pathological patterns often contain the richest low-frequency energy which statistically happens one per frame. Pathological patterns test is also an important indicator of video SFP modules. FS.COM 3Gbps video pathological patterns SFPs are used to transmit optical serial digital signals at the serial rates of SMPTE 259M, SMPTE 344M, SMPTE 292M and SMPTE 424M defined in SMPTE 297-2006. 3Gbps video pathological patterns SFPs with LC interface can transmit optical signals from 50Mbps to 3Gbps reaching the maximum distance of 40km. Both single-mode and multimode video pathological patterns SFPs are available. All modules are hot-pluggable and compatible with SFP MSA. Besides, they can be applied in 3G-SDI/HD-SDI/SD-SDI electrical-optical converter, 3G-SDI/HD-SDI/SD-SDI optical-electrical converter, HD camera or monitor system and high-density digital video routers & switches.



From this article, you must know some information about 3G digital video SFP. Fiberstore offers a full series of low cost but high quality 3G digital video SFPs for your applications covering the link distance of 300 m, 10 km, 20 km, 40 km and 80 km. As the advent of 4K (ultra high definition) market, the demand is growing fast for transporting the 4K in an efficient way. So just expect 6G-SDI or even 12G-SDI products researched and developed by FS.COM.

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