WDM (wavelength division multiplexing)

WDM is a method for multiplexing multiple data on single-core optical fiber cable by changing the wavelength of the carrier wave. There are two modes depending on the multiplexed density: DWDM (dense wavelength division multiplexing) and CWDM (coarse wavelength division multiplexing). DWDM typically uses eight or more wavelengths in the 1.55 um band (some use the 1.3 or 1.6 μm band) that are densely arranged at wavelength intervals from 0.4 to 3.2 nm. In contrast, CWDM uses two to eight wavelengths spaced at wavelength intervals ranging from 20 to several hundred nanometers.

Window material

Window materials commonly used in our devices are described below. The window material must carefully be selected according to the application because the window material determines the spectral response short wavelength cutoff.

  • 1. Borosilicate glass: This is the most frequently used window material. Borosilicate glass transmits radiation from the infrared to approximately 300 nm. It is not suitable for detection in the ultraviolet region.
  • 2. UV-transmitting glass (UV glass): This glass, as the name implies, is ideal for transmitting ultraviolet radiation and is used as widely as a borosilicate glass. The UV cutoff is approximately 185 nm.
  • 3.Synthetic silica (fused quartz): The synthetic silica transmits ultraviolet radiation down to 160 nm and offers lower absorption in the ultraviolet range compared to fused silica.
  • 4.MgF2 (magnesium fluoride): Crystals of alkali halide are superior in transmitting ultraviolet radiation, but have the disadvantage of deliquescence. Among these crystals, MgF2 is known as a practical window material because it offers low deliquescence and transmits ultraviolet radiation down to 115 nm.