Optical Signal Phase Retrieval With Low Complexity DC-Value Method

Abstract

We propose a novel method to reconstruct the optical signal phase information using direct detection. The method is suitable for minimum phase signals and it enables low complexity, low latency, and low tone power operation. Moreover, the proposed method offers low optical complexity solution for the short-reach links compared with the concurrent phase retrieval techniques. We apply the method to M-ary signals with the transmitted power of as low as 3 dBm, and we are able to reach 70 km for 100 Gb/s quadrature phase shift keying (QPSK) system without optical amplification. Our method is based on the single sideband (SSB) and DC-Value property of the minimum phase signal. The SSB and DC-Value properties are iteratively imposed on the amplitude signal in the frequency domain to recover the full complex field from a directly detected optical signal. The normalized mean square error (NMSE) value between the available amplitude information and reconstructed minimum phase signal amplitude decreases after each iteration, providing global minimum convergence. A constant scaling factor is exploited to improve the convergence speed. The scaling factor provides 6 dB, 4.5 dB, and 2.5 dB error vector magnitude (EVM) gains with 4, 5, and 8 iterations, respectively.

Comparison of DC-Value Method and Kramers–Kronig Receiver in Optical OFDM SSB-DD Transmission

“…1. There are various ways to produce OSSB signal, and in this letter the virtual digital carrier-assisted method [19] is considered for the consistent transmission condition in the previous publication [10] [18]. Furthermore, this method can balance the performance and implementation cost, and it also offers precise dynamic CSPR adjustment and utilizes the full bandwidth of the DAC.…”

“…Recently, a DC-Value method [10] has been proposed for reconstructing the optical signal phase using direct detection. It not only overcomes the signal-signal beat interference (SSBI) of SSB-DD system, but also greatly decreases the sampling rate compared to the Kramers-Kronig (KK) receiver [11].…”

A Review of Self-Coherent Optical Transceivers: Fundamental Issues, Recent Advances, and Research Directions

“…Nonetheless, one of the related technical challenges of the conventional KK scheme implementation is the requirement for the DSP block to function at a sampling rate that is faster than the one stipulated by Nyquist. This challenge can be associated with certain nonlinear operations such as the exponential and logarithm functions that are required in the KK algorithm [119]. The associated nonlinear operations can considerably broaden the spectrum of the signal.…”

“…It is noteworthy that an unlimited number of higher harmonics will be generated due to the associated nonlinearities of the operation. Therefore, before executing the nonlinear operations, the output data of the ADC has to be sufficiently upsampled to inhibit aliasing errors [21,[44][45][46]119].…”

“…At the receiver, to recover the field information of the carrier-signal beating, the SSBN can be removed through DSP using either interference cancellation (IC) or any SSBN mitigation scheme, as discussed in Section 4.2. Furthermore, the minimum electrical bandwidth of the receiver is R. Digital chromatic dispersion compensation is supported at the receiver [14,18,29,119].…”