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Impact of Sampling and Quantization on KramersKronig RelationBased Direct Detection
Takaha FUJITA Kentaro TOBA Kariyawasam Indipalage Amila SAMPATH Joji MAEDA
Publication
IEICE TRANSACTIONS on Communications
Vol.E103B
No.11
pp.12911298 Publication Date: 2020/11/01 Publicized: 2020/06/08 Online ISSN: 17451345
DOI: 10.1587/transcom.2019OBP0008 Type of Manuscript: Special Section PAPER (Joint Special Section on Optoelectronics and Communications for Future Optical Network) Category: Keyword: KramersKronig relation, direct detection, digital signal processing, analogtodigital conversion, signalsignal beat interference,
Full Text: FreePDF
Summary:
Impact of sampling frequency and the number of quantization bit of analogtodigital conversion (ADC) in a direct detection lightwave system using KramersKronig (KK) relation, which has been attracting attention in recent years, are numerically investigated. We studied the effect of spectral broadening caused by nonlinear operations (logarithm, square root) of the KK algorithm when the frequency gap (shift frequency) between the modulated signal and the optical tone is varied. We found that reception performances depend on both the ADC bandwidth and the relative positions of the optical tone and the spectrum. Spectral broadening caused by the logarithm operation of the KK algorithm is found to be the dominant factor of signal distortion in an ADC bandwidth limited system. We studied the effect of the number of quantization bit on the error vector magnitude (EVM) of KK relation based reception in a carriertosignal power ratio (CSPR) adjustable transmission system. We found that performances of KK relation based receiver can be improved by increasing the number of quantization bits. For minimumphasecondition satisfied KK receiver, the required number of quantization bit was found to be 5 bits or more for detection of QPSK, 16QAM and 64QAMmodulated signal after 20km transmission.


