Abstract
Based on the principles of crystal birefringence, wave plate phase delay and polarization transformation, a 2×4 90 degree crystal optical hybrid is presented. The beam splitting and coupling between signal and local oscillator lights of the hybrid is realized by two birefringent crystals and two half wave plates, and the required phase shift is produced by a quarter wave plate. Combined with the actual situation, the schemes of phase compensation and power ratio adjustment are given to optimize the performance of the device. And the feasibility of phase compensation and splitter ratio adjustment scheme is simulated and analysed through the establishment of mathematical model according to Jones matrix. The results show that the phase difference and splitter ratio can be set simply and accurately by the scheme of phase compensation and splitter ratio adjustment. Meanwhile, compared with the previous crystal spatial optical hybrid, this hybrid can improve the coupling effect of signal beam and local oscillator beam, and reduce the influence of crystal processing error between in-phase and quadrature branch. It has the advantages of simple and compact structure and good performance, and can be used in free-space optical coherent optical communication system.
Highlights
In the field of satellite-to-ground communication, free space coherent optical communication is the main way to improve the sensitivity of receiver and realize long distance, large capacity and high bit rate laser communication [1,2,3,4,5]
As the key device of coherent optical communication terminal, the purpose of optical hybrid is to split and combine the beam of the signal and local oscillator beams to produce four mixed beams with relative phase shift of 0°, 90°, 180° and 270°, which is convenience to process the subsequent coherent detection information, and its performance has a great influence on the subsequent coherent reception [6,7,8]
The design scheme of the more mature space optical hybrid is mainly to the splitting and coupling is realized by the beam splitter, and the phase difference between the output beams is realized through the wave plate [9,10,11]
Summary
In the field of satellite-to-ground communication, free space coherent optical communication is the main way to improve the sensitivity of receiver and realize long distance, large capacity and high bit rate laser communication [1,2,3,4,5]. The design scheme of the more mature space optical hybrid is mainly to the splitting and coupling is realized by the beam splitter, and the phase difference between the output beams is realized through the wave plate [9,10,11]. These schemes have the shortcomings of too many related components, large insertion loss and difficult to integrate. A crystal optical hybrid which suitable for free space coherent optical communication is designed, and the schemes of phase compensation and split ratio adjustment are
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
