Fiber Optic Tech
Optical transceiver modules are important components in optic fiber communication, converting optic signals into electric signals and vice versa. There are many types of optical transceiver modules, such as SFP, SFP+, QSFP+, QSFP28, CWDM, DWDM modules, etc, each with their own functions and application scenarios. In this article we will introduce about CWDM optical modules and its differences from common types of optical modules.
What is CWDM module
A CWDM module is an optical transceiver module which combines the CWDM technology. CWDM (Coarse Wavelength Division Multiplexer) is a low-cost WDM transmission technology for MAN (Metropolitan Area Network) access layer. In theory, CWDM uses an optical multiplexer at the transmitting end to multiplex optical signals of different wavelengths into one single optical fiber for transmission. At the receiving end of the link, an optical demultiplexer is used to separate the multiplexed signals in the optic fiber into signals of different wavelengths, which are then transmitted to corresponding devices.
CWDM Module vs. Common Modules
(1) CWDM optical modules use fewer optical fibers than common optical modules. CWDM optical modules multiplex the signals of different wavelengths into one channel and transmit them to the receiving end through a single optical fiber. The receiving end demultiplexes the signals into multiple channels of different wavelengths and transmits them to corresponding devices. Common optical modules need one optical fiber for one wavelength. Therefore, CWDM modules can effectively improve the utilization of optical fibers.
(2) CWDM optical modules have 18 wavelengths (1270-1610nm), and each channel has a wavelength interval of 20nm. The wavelengths of common optical modules are 850nm, 1310nm, 1330nm, and 1550nm.
(3) As a low-cost WDM transmission technology for MAN access layer, CWDM is mainly used in telecommunication field, while common optical module is more often used in data communication field.
(4) CWDM optical modules are passive modules, generally adopting the optical planar waveguide technology to divide a beam of light into many rays, while common optical modules are active modules.
Applications of CWDM modules
CWDM optical modules are widely used in CATV (Cable TV), FTTH (Fiber to the Home), 1G and 10G Fibre Channel, 100M and Gigabit Ethernet, Synchronous Optical Network SONET OC-3 (155Mbps), OC-12 (622Mbps) and OC-48 (2.488Gbps), security and protection systems, etc.
Advantages of CWDM modules
(1) Reduce network device and operation cost
(2) Improve the utilization of optical fibers
(3) Small size, low power consumption, with good flexibility and extensibility
Common types and models of CWDM modules
(1) CWDM SFP module
CWDM SFP modules support data rate from 100Mbps to 4.25Gbps, and is widely used in 100M Ethernet, Gigabit Ethernet, 1G/2G/4G Fibre Channel and SONET (Synchronous Optical Network), with maximum transmission distance of up to 120km via single mode fiber.
(2) 10G CWDM SFP+ module
For 10G CWDM SFP+ modules, 18 wavebands are available from 1270nm to 1610nm, with a wavelength interval of 20nm. It is widely used in 10G Ethernet, Optical Transport Network (ONT), 10G CPRI fronthaul, and is compatible with SONET (Synchronous Optical Network) and 10G Fibre Channel, with maximum transmission distance of up to 80 km.
(3) 10G CWDM XFP module
The major difference between CWDM XFP modules and CWDM SFP+ modules lies in their size. CWDM XFP modules are bigger in size and are compliant with XFP MSA protocol, while CWDM SFP+ modules are compliant with IEEE802.3ae, SFF-8431 and SFF-8432 protocols.
(4) 25G CWDM SFP28 module
Widely used in 25G Ethernet and 5G fronthaul, 25G CWDM SFP28 modules transmit via single mode fiber with data rate of 25G and maximum transmission distance of up to 40km.
(5) 40G CWDM QSFP+ module
40G CWDM QSFP+ modules transmit via single mode fiber, with maximum cable distance of 40 km.
Bail latch colors of CWDM modules of different wavelengths
In order to help identify the 18 channel wavelengths of CWDM optic modules, the industry has defined the bail latch color of each wavelength.