The optical signal is input through the injection port of the 1×2 coupler (the light source) onto a measured surface. The light can be backscattered by an object to be analysed, either as it is, or with a shifted wavelength. The reflected light is gathered back through the common fibre (port 3) followed by redirection towards the second port of the coupler to the detector.
High directivity is a great advantage to minimise the light that can directly pass from the injection port to the output port. Also, the insertion loss from port 1 to port 2 is < 6.5dB with a total reflection at the common port. This way, a minimal mismatch between the input and the reflected signal is achieved.
Key features:
- High Directivity > 55dB (with GI 50/125µm).
- Achromaticity and mode insensitivity over the wavelength range 400-1625nm.
- Low insertion loss in round trip configuration ≤ 6.5dB (can be lower than 6dB if not used at fully filled stage).