Use of space-time coding in coherent polarization-multiplexed systems suffering from polarization-dependent loss

Abstract

We evaluate the advantage of using space-time coding in order to increase the tolerance of fiber-optic communications systems to polarization-dependent loss (PDL). Focusing on three particular codes, the Golden Code, the Silver Code (SC), and the Alamouti Code (AC), we calculate the amount of average PDL that can be tolerated for a given signal-to-noise ratio margin that is designed into the system. The SC is shown to be optimal in the case of low to moderate PDL, whereas, in the case of extreme PDL, the AC shows the best performance.

Twin-Wave-Based Optical Transmission With Enhanced Linear and Nonlinear Performances

“…Based on numerical simulations, a Q 2 improvement of 1.2 dB over the conventional PDM-QPSK (without loss of spectral efficiency) was obtained after 5000-km transmission in SSMF [5]. Note that redundancy-free diversity was previously studied to mitigate linear transmission impairments such as polarization-dependent loss [19], and has been extensively studied in the context of wireless multiple-input multiple-output systems [20].…”

Demonstration of an 8-dimensional modulation format with reduced inter-channel nonlinearities in a polarization multiplexed coherent system

“…The resulting constellation alphabet is summarized in Table 1. While the energy and polarization symmetry properties are shared with other space-time block codes, for example, the Alamouti-QPSK format [13], our X-constellation provides an additional 0.53 dB coding gain over existing methods. S 2 ,S 3 ) (0,4,0) (0,0,4) (0,0,-4) (0,-4,0) (0,0,-4) (0,4,0) (0,-4,0) (0,0,4) (0,0,4) (0,-4,0) (0,4,0) (0,0,-4) (0,-4,0) (0,0,-4) (0,0,4) …”

Optical implementation of a space–time-trellis code for enhancing the tolerance of systems to polarization-dependent loss

“…Space-time coding [1] is a natural approach, and the Golden and Silver codes that were studied in the context of PDL so far [2,3] were predicted to increase the tolerable amount of PDL by approximately 2 dB (assuming standard PDL margin levels of 1-2 dB). The main drawback of these codes, which were designed for the wireless communications environment, is the decoder's complexity, which notably increases the overall complexity of the receiver.…”

“…Figure 2(b) shows the required margin as a function of the average PDL for the uncoded system and with the proposed code implemented with τ T s and ZF equalization. The results of the Golden and Silver codes (with optimal decoding) were reproduced from [3] for comparison. The inferiority of the proposed scheme is negligible when the mean PDL is 1 dB or lower and grows to approximately 1.5 dB for 3 dB of average PDL.…”

“…(b) Required margin versus mean PDL with the Silver and Golden codes, the proposed code (with τ T s ), and in the uncoded case. Silver and Golden code results were copied from [3].…”