Virtually Isotropic Transmission Media With Fiber Raman Amplifier

Abstract

-We report a theoretical study and simulations of a novel fiber-spin tailoring technique to suppress the polarization impairments, namely polarization mode dispersion (PMD) and polarization dependent gain (PDG), in fiber Raman amplifiers. Whereas use of depolarizer or multiplexing pump laser diodes with a final degree of pump polarization of 1% for periodically spun fiber results in PDG of about 0.3 dB, we demonstrate that application of just a two-section fiber (where the first part is short and has no spin, and the second one is periodically spun) can reduce the PDG to as low as below 0.1 dB.

Two-Section Fiber Optic Raman Polarizer

“…Varying signal SOPs at the input of fiber Raman amplifier leads to uncontrollable output gain variation. Maximum of the gain variation is defined as polarization dependent gain (PDG) [4][5][6][7][8]. Traditional PMD suppression technique is based on spinning the fiber periodically and results in PMD suppression below 0.04 ps/km 1/2 [2,3].…”

“…Traditional PMD suppression technique is based on spinning the fiber periodically and results in PMD suppression below 0.04 ps/km 1/2 [2,3]. However, this PMD suppression is accompanied with a simultaneous increase in the Raman PDG [5][6][7][8]. The new approach developed by Sergeyev et al [7,8] have shown that it is possible to simultaneously mitigate both PDG and PMD by using a fiber with a particular spin profile or, more specifically, a two-section fiber ('two-section approach') in which the first section has no spin and the second one is periodically spun.…”

“…However, this PMD suppression is accompanied with a simultaneous increase in the Raman PDG [5][6][7][8]. The new approach developed by Sergeyev et al [7,8] have shown that it is possible to simultaneously mitigate both PDG and PMD by using a fiber with a particular spin profile or, more specifically, a two-section fiber ('two-section approach') in which the first section has no spin and the second one is periodically spun. A new approach based on using anisotropy of Raman amplification (Raman polarizer) to repolarize and amplify signal rather than to depolarize it has been recently developed by Martinelli et al [9] , Kozlov et al [10] and Ursinini et al [11].…”

“…The results show that the two-section fiber provides better characteristics as compared to other approaches and so can be used in highspeed fiber optic communication systems for design of spatially and spectrally transparent media with an increased Raman gain [12,13] and pump losses, respectively s 0 (z) is the part of the signal amplitude related to pump-signal SOPs interaction. The part of the Raman gain ∆G related to polarization evolution due to random birefringence and fiber spinning depends on s 0 as follows [5][6][7][8]:…”

“…Two-section Fiber Optic Raman Polarizer Sergey Sergeyev, Sergei Popov P If the input pump and signal SOPs are parallel, the Raman gain takes the maximum value and if the SOPs are orthogonal then Raman gain takes the minimum one [4][5][6][7][8]. The difference in the gain (polarization dependent gain, PDG) and mean-square gain fluctuations (MSGF) σ can be found as follows [5][6][7][8] ( )…”