Polarization Dependent Gain Stability of Raman Amplification Single-Core Feedback Structure Based on Consistency of Long-Axis Azimuths Variation

• Published in: Photonics Vol. 10; no. 12; p. 1294
• Main Authors: Yu, Fengzhen, Ma, Yixiao, Jia, Kun, Lai, Xin, Xiao, Qian, Jia, Bo
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-12-2023
• Subjects: Amplification; Amplifiers; Azimuth; Consistency; Ellipticity; Faraday rotating mirror; Feedback; Optical communication; Optical paths; Output feedback; Polarization; Radio frequency; Raman fiber amplifier; Rotating mirrors; single-core feedback structure; Stability analysis; Variation; Wave division multiplexing
• DOI: 10.3390/photonics10121294
• EISSN: 2304-6732

The law of the polarization state of Raman fiber amplifier switch in single-core feedback structures is unknown. In this paper, two kinds of optical paths with single-core feedback structures are constructed, namely the Raman amplified Faraday rotating mirror single-core feedback structure (RFA-FRMOP) and the Raman amplified ordinary flat mirror single-core feedback structure (RFA-RMOP). In the process of optical signal amplification involving Raman fiber amplifiers, the polarization dependent gain (PDG) generated by Raman switches is affected by the polarization state, and RFA-FRMOP shows better stability. Surprisingly, polarization analysis of the RFA-FRMOP structure shows that both the ellipticity angle and the long-axis azimuth of the output feedback structure changed less than that of the signal entering the feedback structure. The consistency of the long-axis azimuth variation is the main characteristic of the RFA-FRMOP structure. It is found that the variation of the azimuth of the long axis of the RFA-FRMOP structure is obviously greater than that of the ellipticity. These conclusions provide a theoretical basis for the polarization dependent application of Raman fiber amplifiers in single-core feedback structures.