High-performance single-mode fiber polarization-independent isolators

The design and performance of polarization-independent isolators that are substantially insensitive to variations of temperature and wavelength are presented. Three single-mode fiber isolators have been designed, constructed, and tested. The first isolator is a 1.3-microm two-stage isolator that has more than 40 dB of isolation and less than 2.0 dB of insertion loss over the temperature range of 15-70 degrees C. The second isolator is a two-stage dual-wavelength isolator with an insertion loss of less than 4 dB and an isolation of better than 35 dB at 1.3 and 1.52 microm over the temperature range of 15-75 degrees C. The third isolator is a three-stage isolator with an insertion loss of less than 2.5 dB and an isolation of better than 63 dB over the wavelength range 1275-1355 nm.