Recent Developments and Applications of Polarization-Maintaining Fiber Loop Mirrors

Reflective Semiconductor Optical Amplifier Direct Modulation Capability Enhancement Using Birefringent Fiber Loop

“…The total PMF length, L ≈ 8.5 m, resulted in the periodic comb-like transfer function shown in Figure 7a, which comprised of maxima (peaks) and minima (notches) repeated every ≈0.87 nm (Figure 7b), equal to the BFL free spectral range (FSR = λ 2 /BL). Setting the PC to generate a rotation of 90 • to beams coming from both loop directions [34] optimized the amplitude difference between peaks and notches, or the peak-to-notch contrast ratio (PNCR), to 22 dB (Figure 7c). To enhance stability against environmental perturbations by affordable means, the whole construction was enclosed inside a box, which was placed on a marbled base.…”

Performance improvement of directly modulated semiconductor optical amplifier with filter‐assisted birefringent fiber loop

“…After passing through an isolator to block undesirable back reflections and a 0.22 nm‐bandwidth fiber grating‐type optical bandpass filter, OBPF1 (JDSU model TB9) to reject SOA noise outside the signal band, the modulated light was inserted in the BFL. The BFL was constructed using a polarization maintaining (PM) 3‐dB coupler, and a PC set to generate a rotation of 90° to beams coming from both directions and a segment of polarization maintaining fiber (PMF) with birefringence 3.3 × 10 −4 at 1540 nm, which resulted in a total PMF length of 8.5 m and loss ∼8.5 dB. Finally, the signal that emerged from the BFL was launched into a cascaded thin film‐based optical bandpass filter, OBPF2 (JDSU model TB4500), with operating range 1530–1560 nm, 3‐dB bandwidth 1.3 nm, and loss ∼5 dB when centered around 1540 nm.…”

“…The BFL acts as comb filter that mitigates the pattern‐dependent fluctuations of the transient chirp induced due to the SOA direct current modulation and improves the quality of the encoded optical signal. The BFL has several attractive features , which allow it to favorably compete with other filtering schemes exploited for the same goal . In this letter, we extend this work by proposing to assist in an efficient and affordable manner the operation of the BFL using an optical bandpass filter (OBPF).…”