A Wavelength Selective Coupler (WSC) is an optical device that is used to couple the pump laser wavelength to an optical fiber while blocking out all other interfering wavelengths. This device is most often used in Erbium-doped fiber amplifiers (EDFA), which are used in communication systems to amplify optical signals.
A WSC works by using a special type of optical filter, known as a wavelength division multiplexer (WDM). This filter is designed to allow only the pump laser wavelength to pass through the device, while reflecting all other wavelengths back into the source. This is achieved by engineering the filter’s refractive index to match the laser wavelength. This allows the laser to be coupled to the optical fiber, while ensuring that all other wavelengths are blocked.
The main purpose of a WSC is to ensure that the pump laser wavelength is delivered to the EDFA with minimal loss or interference. This ensures that the EDFA will function at peak efficiency and provide the highest levels of signal amplification. Without the WSC, other wavelengths would interfere with the operation of the EDFA, reducing the level of signal amplification. Additionally, the WSC helps to protect the EDFA from damage caused by high-power laser sources, as the device is engineered to absorb most of the excess power.
In summary, a WSC is an essential component of any EDFA-based communication system. The device is designed to couple the pump laser wavelength to the optical fiber while filtering out all other unwanted wavelengths. This ensures that the EDFA will function at peak efficiency and provide the highest levels of signal amplification. Additionally, the WSC also helps to protect the EDFA from high-power laser sources.