Quantization Error Improvement for Optical Quantization Using Dual Rail Configuration

Tomotaka NAGASHIMA  Makoto HASEGAWA  Takuya MURAKAWA  Tsuyoshi KONISHI  

IEICE TRANSACTIONS on Electronics   Vol.E98-C   No.8   pp.808-815
Publication Date: 2015/08/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E98.C.808
Type of Manuscript: Special Section PAPER (Special Section on Microwave Photonics)
Category: Optical A/D Conversion
photonic analog-to-digital conversion,  optical signal processing,  soliton self-frequency shift (SSFS),  self-phase modulation (SPM),  effective number of bits (ENOB),  

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We investigate a quantization error improvement technique using a dual rail configuration for optical quantization. Our proposed optical quantization uses intensity-to-wavelength conversion based on soliton self-frequency shift and spectral compression based on self-phase modulation. However, some unfavorable input peak power regions exist due to stagnations of wavelength shift or distortions of spectral compression. These phenomena could induce a serious quantization error and degrade the effective number of bit (ENOB). In this work, we propose a quantization error improvement technique which can make up for the unfavorable input peak power regions. We experimentally verify the quantization error improvement effect by the proposed technique in 6 bit optical quantization. The estimated ENOB is improved from 5.35 bit to 5.66 bit. In addition, we examine the XPM influence between counter-propagating pulses at high sampling rate. Experimental results and numerical simulation show that the XPM influence is negligible under ∼40 GS/s conditions.