It generally refers to the highly birefringent polarization maintaining fibers used to manufacture fiber optic gyroscope (FOG) coils. These fibers must offer particular optical and mechanical performance to make them suitable for the application. A gyroscope creates an optical interference between two light beams propagating in opposite directions around a fiber coil. When the coil is rotated, the phase of the light beams shifts relative to each other an dmoves out of step. In order to avoid noise signals from spurrious mixing of non-contributing parts of the beam, the light is single-mode and also single polarization. It is to maintain this particular polarization state of the light that HiBi polarization maintaining fiber is required. Furthermore, the gyro coils tend to be very long, up to a km or even more (gyro coils of up to 10 km have been designed), so the fiber must be suited to being coiled into long lengths at diameters as small as a few centimeters. For this reason a reduced cladding fiber providing low-attenuation and strong guidance is required. In addition to this , the environments the fiber must withstand are often very harsh and gyroscope fiber is specifically designed to perform over a very wide temperature range (typically from -55oC ro +85oC) and under serious vibration levels.
Fibercore offers a wide range of HiBi Bow-Tie PM Gyro fibers with short beat length and radiation tolerance for space applications.