Course Wavelength Division Multiplexing, or CWDM, is a cost-effective method to scale connections over existing fiber infrastructure.
Passive CWDM networks can support point-to-point connections or point-to-multipoint connections for fiber rings or add/drop application.
CWDM transmits up to 18 connections spaced at 20nm increments over the optical spectrum, (between 1271nm and 1611nm). The optical spacing enables CWDM to transmit and receive up to 18 channels over a fiber pair.
The longest eight wavelengths, 1471nm ~ 1611nm are the most commonly used in optical communications networks as they provide the best optical performance over distance (up to 160km @1G) and data rates (10G).
| Wavelengths | Data Rate/Form Factor | Distance/Reach |
|---|---|---|
| 1271, 1291, 1311, 1331, 1351, 1371, 1391, 1411, 1431, 1451 | SFP – 1G SFP+ - 10G XFP – 10G | Up to 40Km Up to 40KM Up to 40KM |
| 1471, 1491, 1511, 1531, 1551, 1571, 1591, 1611 | SFP – 1G SFP+ - 10G XFP – 10G | Up to 160KM Up to 80KM Up to 80KM |
The distance between locations is a function of the by the optical budget of the CWDM transceivers and the loss budget in the fiber optic network. CWDM transmission cannot be amplified, so planning an upgrade strategy from 1G to 10G is very important.
The ITU G.694.2 CWDM grid was revised in 2003 to shift the center wavelength one nanometer. The official ITU grid now reads 1471, 1491, 1511, etc., rather than the common commercial reference of 1470, 1490, 1510 etc. All typical CWDM transceivers are in compliance with the current ITU center wavelength requirements (1471, 1491, 1511, etc.) despite being referred to as 1470, 1490, etc.