High precision measurement technology for beat length of birefringence optical fiber

摘要

We propose a precision and flexible measurement method for the beat length of birefringence optical fiber (BOF) with a hybrid Sagnac interferometer formed with a single mode fiber directional coupler and BOFs. The measurement error equation was obtained based on error estimation theory and it was found that there is an optimum length for certain BOF under test. The measurement error can be less than 0.001 mm with 1 pm wavelength precision and 0.1 mm fiber length precision. With a high performance wavelength interrogator technology and a special designed fiber length measurement method, a beat length measurement setup was built and the measurement standard deviation of 3.08 × 10~(-4) mm was achieved with 250 measurement samples for solid core polarization maintaining photonic crystal fibers (PM-PCFs). The beat length stability of two PM-PCFs with different structure sizes has been measured and compared. The result demonstrated that the birefringence temperature characteristic of the PM-PCFs may be dependent on structure sizes.