Why GE CWDM Products Using Uncooled Lasers Don't Support Industrial Temperature Applications

⦁ Background

1GE CWDM modules using uncooled DFB lasers are only suitable for commercial-temperature applications. This article analyzes the core reasons for this limitation.

International Standards for CWDM Products

⦁ ITU-T Recommendation G.694.2 defines the nominal center wavelengths and channel bandwidths for CWDM systems.

A total of 18 standardized wavelengths are specified, with 20 nm channel spacing and a maximum allowed center wavelength offset of ±6.5 nm from the nominal value.

Table 1 Nominal CWDM Center Wavelengths (ITU-T G.694.2, 20 nm spacing)

G.6942 Nominal central wavelengths (nm)for spacing of 20 nm
G.6942 Nominal central wavelengths (nm)for spacing of 20 nm
1271
1291
1311
1331
1351
1371
1391
1411
1431
1451
1471
1491
1511
1531
1551
1571
1591
1611

⦁ Temperature Characteristics of DFB Lasers

The center wavelength of a DFB laser shifts positively with rising temperature and negatively with falling temperature.

According to datasheets from mainstream DFB CWDM chip vendors (including AOI, Broadcom, and Hisense Optoelectronics), the typical wavelength-temperature coefficient is 0.09 nm/°C, with a center wavelength tolerance of ±3 nm at 25°C (room temperature).

Table 2 Nominal Center Wavelength Ranges of AOI 2.5G CWDM DFB Lasers

Part Number	Center wavelength minimum(nm)	Center wavelength(nm)	Center wavelength maximum(nm)
DFB-1470-T5-2.5-A7-A-A-M787	1467	1470	1473
DFB-1490-T5-2.5-A7-A-A-M787	1487	1490	1493
DFB-1510-T5-2.5-A7-A-A-M787	1507	1510	1513
DFB-1530-T5-2.5-A7-A-A-M787	1527	1530	1533
DFB-1550-T5-2.5-A7-A-A-M787	1547	1550	1553
DFB-1570-T5-2.5-A7-A-A-M787	1567	1570	1573
DFB-1590-T5-2.5-A7-A-A-M787	1587	1590	1593
DFB-1610-T5-2.5-A7-A-A-M787	1607	1610	1613
NOTE : ALL wavelength ate tested in T=25℃,P0=5mW,CW mode

⦁ Core Analysis

Taking the 1470 nm wavelength as an example:

⦁ At a high industrial temperature of 85°C, the center wavelength drifts to:

1473 + 0.09 × (85 − 25) = 1478.4 nm

⦁ This value exceeds the maximum allowable center wavelength defined by ITU-T G.694.2:

1471 + 6.5 = 1477.5 nm

The fundamental reason uncooled 1GE CWDM modules cannot support industrial-temperature applications is that the DFB laser wavelength drifts significantly with temperature. At extreme high temperatures, the wavelength drifts outside the standardized CWDM channel bandwidth.

For industrial-temperature environments, Moduletek offers 1GE CWDM products equipped with temperature-cooled lasers to stabilize the wavelength.

Moduletek provides:

⦁ Commercial-temperature 1GE CWDM modules with uncooled lasers

⦁ Industrial-temperature 1GE CWDM modules with cooled lasers

For further inquiries about the above content, please contact us at: sales@moduletek.com

Back

PREVIOUS：Relationship Between Link Budget And Transmission Distance In Optical Modules

NEXT：How To Enable Support For Third-Party Modules On Arista Switches

Hot Recommended

Why GE CWDM Products Using Uncooled Lasers Don't Support Industrial Temperature Applications