Fig. 1. SOP variation within a beat length.

Fig. 2. Improved fusion method of manufacturing all-fiber QWPs.

Fig. 3. Beat length measurement system. (a) Observation with the microscope birefringence measurement instrument, and (b) the retardances and birefringence calculations of three samples.

Fig. 4. Three different types of all-fiber QWP samples. (a) TYDSF, (b) PANDA-type PMF, and (c) elliptical-core PMF.

Fig. 5. (a) System of SOP measurement; (b) variation tendency of ellipticity of the TYDSF QWP sample with vibration at 1310 nm. CL, collimating lens; P1, first polarizer; Q, quarter-wave plate; P2, second polarizer; L, lens; PA, polarization analyzer.

Fig. 6. Temperature sensitivity testing system. (a) PER measurement part and (b) ellipticity measurement part. TCC, temperature control chamber; P, polarizer; PM, power meter.

Fig. 7. Trend of PER and ellipticity of the TYDSF QWP sample with temperature.

Fig. 8. Comparison of the variation tendency of PER and ellipticity of three different samples with temperature.

Fig. 9. TYDSF QWP device used in a high-power laser system. SBM, spectral broadening module; ISO, optical isolator; LD, laser diode; MFA, mode field adapter; CPS, cladding power stripper; YDF, ytterbium-doped fiber; QBH, quartz block housing.