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Introduction to the differences between gray light Modules and color light Modules

Time: 2023-12-13
        ⦁ Background
        We often hear about gray light module and color light module, what are the differences in their characteristics and applications? The following is a brief chat.
        ⦁ Wavelength window for optical communication
        The first window of 850nm, the second window of 1310nm, the third window of 1550nm and the fourth window of 1625nm are used for optical communication, as shown in the figure below:
Wavelength windows for optical communication and attenuation in optical fiber
Figure 1 Wavelength windows for optical communication and attenuation in optical fiber
        From the above figure, it can be seen that the wavelength for optical communication is mainly 850-1625nm, while the wavelength of light visible to the naked eye (red, orange, yellow, green, blue, blue and purple) is mainly distributed in the 780-380nm, so the gray and colored light module does not mean that the light module emits a gray or colored.
        ⦁ Definition and difference between gray and colored light modules
        Gray light module (Grey): the wavelength is fluctuating within a certain range, there is no specific standard wavelength, such as the customer side of the wavelength division equipment optical port, the corresponding interface is called gray light interface.
        Color light module (Color): wavelength fluctuations in a very small range near the center wavelength, can be connected to the combined wave device, with a standard wavelength, wavelength division system in the line veneer wavelength division side of the optical signal, the corresponding interface is called a color light interface.
        Color optical module according to the different wavelength density can be divided into CWDM (coarse wavelength division multiplexing) optical module and DWDM (dense wavelength division multiplexing) optical module, color optical module ride with the wavelength of the wave will be synthesized with different wavelengths of the optical signal all the way to transmission, greatly reducing the link cost.
        The following figure briefly describes the application scenarios of gray light and color light modules:
gray light and color light module application scenarios
Figure 2 gray light and color light module application scenarios
        A brief summary of the differences between gray light and color light modules, the following table:
Table 1 gray light and color light module differences
 Optical module type
 Gray Optical module
 Color Optical module
 Wavelength
 Center wavelength range:   approximately ±30nm
 CWDM center wavelength range: ±6.5nm   DWDM/100GHZ center wavelength range: ±0.04nm
 Application
 Mostly used on the customer   side
 Mostly used on the line side
 Characteristics
 Low power consumption,   suitable for short-distance   transmission
 Large bandwidth capacity, saving fiber resources
 Standard   Compliance
 ITU-T G.957 ITU-T G.959.1   IEEE802.3
 ITU-T G.694.1（DWDM）ITU-T G694.2（CWDM）
 Product  Example
  SFP-OC3-IR1
  SFP-GE-SX
  SFP-10G-LR
  SFP28-25G-SR
  SFP-GE-CWDM-1470
  SFP-10G-ZR-CWDM-1550
  SFP-10G-ZR-DWDM-P57-1531.90
  SFP28-25G-LR-CWDM-1330

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