160 Gbps WDM Transmission System using Linearized SOA with 50 GHz Channel Spacing

Abstract

In a 16 Channel, 10 Gbps WDM System with Linearized SOA using feed forward linearization technique the effect of reduced channel spacing has been investigated. The basic mechanism of crosstalk is completely independent of the amplifier but it depends on the spectral overlap of adjacent channel. However In this paper it has been validated that using linearized SOA the system can be extended to 120 Km length with channel spacing as small as 50 GHz. The achieved QFactor was 11 at 100km and 4.2 at 120Km.

Performance of feed‐forward linearizers of power amplifiers in OFDM systems under complex gain errors

“…A conceptual diagram of an adaptive FF linearization system is shown in Figure 1 [28]. As shown in Figure 1, the FF linearization circuit consists of two loops; the first is used for canceling the main signal (x(t)), while the second is used for canceling the distortion component of the output of the main amplifier.…”

“…Although this approach reduces the nonlinear effects substantially, it comes at the expense of decreased power efficiency, which is unfavorable. To overcome this problem, adaptive FF linearizers based on digital signal processing (DSP) have been proposed in the literature to compensate for the high sensitivity to device imperfections and parameter errors [27][28][29][30][31][32] by adaptively controlling vector modulators used to provide these gains. Out of these techniques, FF linearization has been the most attractive approach in OFDM systems because of the wideband nature of the analog circuitry used in manipulating the signals in the FF implementation [21][22][23][24][25][26][27][28].…”

“…The second approach is to use a linearization technique such as predistortion, feed-forward (FF), feedback, and envelope elimination and restoration approaches [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Out of these techniques, FF linearization has been the most attractive approach in OFDM systems because of the wideband nature of the analog circuitry used in manipulating the signals in the FF implementation [21][22][23][24][25][26][27][28]. The operation of the FF techniques is basically concerned with canceling the distortion signal.…”

“…Imbalances in these complex gains result in imperfect signal cancelation, which compromises the overall performance of the FF system. To overcome this problem, adaptive FF linearizers based on digital signal processing (DSP) have been proposed in the literature to compensate for the high sensitivity to device imperfections and parameter errors [27][28][29][30][31][32] by adaptively controlling vector modulators used to provide these gains. However, DSP-based estimation of the complex gains can further result in gain errors because of the various elements used in the downconversion of signals to baseband as well as the convergence issues of the DSP algorithms [30].…”