Difference between CWDM optical transceiver module and DWDM optical transceiver module

With the rapid growth of IP data services on the Internet, the demand for transmission line bandwidth is increasing. Although DWDM optical module (dense wavelength division multiplexing) technology is the most effective method to solve line bandwidth expansion, CWDM optical module (coarse wavelength division multiplexing) technology has advantages in system cost and maintainability compared to DWDM optical modules. .

Both the CWDM optical module and the DWDM optical module belong to the wavelength division multiplexing technology, and can couple different wavelengths of light into a single-core optical fiber for transmission.

The latest ITU standard for CWDM optical modules is G.695, which specifies 18 wavelength channels with a spacing of 20 nm from 1271 nm to 1611 nm. Considering the water peak effect of ordinary G.652 fiber, 16 channels are generally used. Because the channel spacing is large, both the multiplexer and the laser are cheaper than the DWDM device.

The channel spacing of DWDM optical modules is 0.4 nm, 0.8 nm, 1.6 nm, etc., and the spacing is small, requiring additional wavelength control devices. Therefore, devices based on DWDM technology are more expensive than devices based on CWDM technology.

The CWDM optical module has 18 bands, from 1270nm to 1610nm, with a spacing of 20nm between each band. The CWDM optical channel has a wide spacing. The CWDM optical modulation uses an uncooled laser, which is electronically tuned to multiplex the optical wavelength ratio on the same fiber. DWDM is less, the reason for the "rough" and "dense" titles is here.

DWDM optical modules are available in three channels per channel as required: 0.4nm (50Ghz), 0.8nm (100Ghz), and 1.6nm (200Ghz), 100GHz (from C17 to C61, which is the most commonly used for conventional equipment); 50GHz (From C17 to H61, for high channel devices). DWDM uses a cooling laser that is tuned with temperature.

Since the temperature distribution is very uneven over a wide range of optical wavelengths, temperature tuning is difficult and costly to implement. The CWDM optical module avoids this difficulty and thus greatly reduces the cost. At present, the cost of the CWDM optical module system is generally only 30% of that of the DWDM, and the CWDM wavelength of 1470 nm to 1610 nm generally uses the DFB laser. Because of the large channel spacing, the CWDM device and the laser ratio are DWDM devices are cheap.