Wavelength corresponding to the light source of the optical module

Optical modules typically use central wavelengths of 850nm, 1310nm, or 1550nm, depending on transmission distance and fiber type.Central WavelengthsThe central wavelength of an optical module refers to the midpoint of the optical signal spectrum emitted by the light source, usually a laser diode (LD) or light-emitting diode (LED), measured in nanometers (nm) . The most commonly used wavelengths are:850nm: Short wavelength window, primarily used for short-distance transmissions (up to 500 meters) over multimode fiber .1310nm: Long wavelength window, suitable for medium-distance transmissions (500 meters to 20 km) over single-mode fiber .1550nm: Long wavelength window, ideal for long-distance transmissions (20 km to 40 km or more) due to minimal fiber loss . Additional wavelength ranges include CWDM (1270–1610nm) and DWDM (1525–1565nm or 1570–1610nm) for dense wavelength-division multiplexing applications .Factors Affecting Wavelength SelectionTransmission Distance: Shorter wavelengths like 850nm are used for short links, while 1310nm and 1550nm are preferred for longer distances due to lower fiber attenuation .Fiber Type: Multimode fibers typically use 850nm, whereas single-mode fibers use 1310nm or 1550nm .Optical Loss: Fiber loss decreases with increasing wavelength up to 1550nm, making it optimal for long-haul communication .Module Type: The light source type (LD or LED) and modulation rate also influence the exact central wavelength .SummaryIn practice, optical modules are designed with a specified central wavelength range to ensure compatibility with fiber types and transmission distances. The 850nm, 1310nm, and 1550nm bands remain the standard for most commercial optical modules, with CWDM and DWDM wavelengths used for multiplexed systems . This selection ensures efficient signal transmission, minimal loss, and optimal network performance.