A 90 degrees optical fiber hybrid for optimal signal power utilization

Broadband free space 2 × 4 90° optical hybrid for satellite laser communication

We design a broadband free space 2×4 90° optical hybrid over a spectral window of 1000-1200 nm and 1470-1650 nm and verify the feasibility of the scheme experimentally. The hybrid consists of three broadband polarization beam splitters, an achromatic λ/4 wave plate, and three achromatic λ/2 wave plates. The fabricated hybrid exhibits a good quadrature phase response with an interchannel imbalance of 0.93-1.07 and a low phase deviation of less than 0.2° under the typical communication wavelengths of 1064 nm and C-band. The experimental results of the heterodyne method show that the proposed hybrid can effectively solve the wavelength incompatibility problem in satellite laser communication and realize interconnection at different wavelengths. The designed hybrid (without coupling) has a measured insertion loss of no more than 7.34 dB at 1064 nm and C-band. A high-speed transmission experiment with BPSK format has been conducted to verify the performance of the assembled device.

All-fiber Fabry-Pérot interferometer for reducing noise on the basis of differential structure

In this study, we propose a new optical fiber interferometer based on differential structure. The phase delay exists in the two output arms of the coupler. When the interference signal passes through the phase delay twice in the transmission, it produces a phase shift of π with the original signal. This feature can be used to differentially reduce noise. The experimental results show that the signal-to-noise ratio increases by 1.29 dB, and the waveform of the reconstructed signal is reduced by 12 nm. Thus, the structure can effectively improve the quality of the measured signal.