Definition Of Wavelength Division Multiplexing

March 14. 2016

With the optical fiber application develop, the CWDM and DWDM was designed in the optical network . The early fiber optic transmission systems put information onto strands of glass through simple pulses of light. A light was flashed on and off to represent the “ones” and “zeros” of digital information. The actual light could be of almost any wavelength (also known as color or frequency) from roughly 670nm to 1550nm. We have Qlogic 10G XFP CWDM TRANSCEIVER for you!
Currently, there are two types of WDM in existence today: Coarse WDM (CWDM) and Dense
WDM (DWDM). Backwards as it may seem, DWDM came well before CWDM, which appeared only after a booming telecommunications market drove prices to affordable lows. Whereas CWDM breaks the spectrum into big chunks, DWDM dices it finely. DWDM fits 40-plus channels into the same frequency range used for two CWDM channels.
CWDM is defined by wavelengths. DWDM is defined in terms of frequencies. DWDM’s tighter wavelength spacing fit more channels onto a single fiber, but cost more to implement and operate.
As the need for information increased, the need for bandwidth also increased. Early SONET systems used 1310nm lasers to deliver 155 Mb/s data streams over very long distances. But this capacity was quickly exhausted. Advances in optoelectronic components allowed design of systems that simultaneously transmitted multiple wavelengths of light over a single fiber. Multiple high-bit rate data streams of 2.5 Gb/s, 10 Gb/s and, more recently, 40 Gb/s and 100Gb/s could be multiplexed through divisions of several wavelengths. And so was born Wavelength Division Multiplexing (WDM).
CWDM - Coarse Wavelength Division Multiplexing. WDM systems with fewer than eight active wavelengths per fiber. The wavelength is including 1270nm, 1290nm,1310nm, 1330nm, 1350nm, 1370nm, 1390nm, 1410nm, 1430nm, 1450nm, 1470nm, 1490nm, 1510nm, 1530nm, 1550nm, 1570nm, 1590nm, 1610nm .
DWDM - Dense Wavelength Division Multiplexing. WDM systems with more than eight active wavelengths per fiber.
Distinctive CWDM differences
CWDM can—in principle—match the basic capabilities of DWDM but at lower capacity and lower cost. CWDM enables carriers to respond flexibly to diverse customer needs in metropolitan regions where fiber may be at a premium. However, it’s not really in competition with DWDM as both fulfill distinct roles that largely depend upon carrier-specific circumstances and requirements anyway. The point and purpose of CWDM is short-range communications. It uses wide-range frequencies and spreads wavelengths far apart from each other. Standardized channel spacing permits room for wavelength drift as lasers heat up and cool down during operation. By design, CWDM equipment is compact and cost-effective as compared to DWDM designs.
Distinctive DWDM differences

DWDM is designed for long-haul transmission where wavelengths are packed tightly together. Vendors have found various techniques for cramming 32, 64, or 128 wavelengths into a fiber. When boosted by Erbium Doped-Fiber Amplifiers (EDFAs)—a sort of performance enhancer for high-speed communications—these systems can work over thousands of kilometers. Densely packed channels aren’t without their limitations. First, high-precision filters are required to peel away one specific wavelength without interfering with neighboring wavelengths. Those don’t come cheap. Second, precision lasers must keep channels exactly on target. That nearly always means such lasers must operate at a constant temperature. High-precision, high-stability lasers are expensive, as are related cooling systems.

ITU Channel Product Code	Frequency(THz)	Wavelength(nm)	ITU Channel Product Code	Frequency(THz)	Wavelength(nm)
17	191.7	1563.86	40	194	1545.32
18	191.8	1563.05	41	194.1	1544.53
19	191.9	1562.23	42	194.2	1543.73
20	192	1561.42	43	194.3	1542.94
21	192.1	1560.61	44	194.4	1542.14
22	192.2	1559.79	45	194.5	1541.35
23	192.3	1558.98	46	194.6	1540.56
24	192.4	1558.17	47	194.7	1539.77
25	192.5	1557.36	48	194.8	1538.98
26	192.6	1556.55	49	194.9	1538.19
27	192.7	1555.75	50	195	1537.4
28	192.8	1554.94	51	195.1	1536.61
29	192.9	1554.13	52	195.2	1535.82
30	193	1553.33	53	195.3	1535.04
31	193.1	1552.52	54	195.4	1534.25
32	193.2	1551.72	55	195.5	1533.47
33	193.3	1550.92	56	195.6	1532.68
34	193.4	1550.12	57	195.7	1531.9
35	193.5	1549.32	58	195.8	1531.12
36	193.6	1548.51	59	195.9	1530.33
37	193.7	1547.72	60	196	1529.55
38	193.8	1546.92	61	196.1	1528.77
39	193.9	1546.12