Differential Detection Receiver Research Articles

Carrier-assisted differential detection receiver with low carrier-to-signal power ratio employing parallel multi delay

We propose a parallel multi delay (PMD) carrier-assisted differential detection (CADD) receiver for the first time, including PMD asymmetric-CADD (PMD A-CADD) and PMD symmetric-CADD (PMD S-CADD). The transfer function of the PMD CADD receiver is optimized by expanding the number of optical delays to a general selection, thereby suppressing the signal-signal beat interference (SSBI). As a result, the required carrier-to-signal power ratio (CSPR) is reduced, and the optical signal-to-noise ratio (OSNR) sensitivity is drastically improved. Two schemes for further mitigation of residual SSBI are introduced, namely SSBI iterative cancellation algorithm and the increased guard band mitigation method. For SSBI iterative cancellation algorithm, by optimizing the number of optical delays, the optimal CSPR for the P6D A-CADD and the P5D S-CADD can be reduced to −1 dB, the required number of iterations is only 3, and compared with the parallel dual delay-based asymmetric-CADD (PDD A-CADD) receiver, the OSNR sensitivity is improved by about 4.5 dB. For the increased guard band mitigation method, 2.34 GHz and 3.16 GHz guard band are required for the P6D A-CADD and the P5D S-CADD to meet the 7% FEC threshold at 0 dB CSPR.

Research Progress on Carrier-Free Phase-Retrieval Receivers

In order to deal with the chromatic dispersion-induced power fading issue for short-reach direct-detection optical fiber communication applications, such as the ever-increasing data-center interconnections (DCIs), optical filed recovery is intensively being under investigation. To date, various direct detection schemes capable of optical field recovery have been proposed, including the Kramers–Kronig (KK) receiver, asymmetric self-coherence detection (ASCD) receiver, carrier-assisted differential detection receiver (CADD), Stokes vector receiver (SVR), and carrier-free phase-retrieval (CF-PR) receiver. Among those, the CF-PR receiver attracts lots of research attention because it can circumvent the requirement of a strong continuous-wave (CW) optical carrier for the beating with the signal. Generally, the CF-PR receiver consists of only two single-ended photodiodes (PDs) and one dispersive element, for the field recovery of the quadrature amplitude modulation (QAM) signals. Based on the theoretical and experimental studies reported so far, this paper reviews the latest progress of CF-PR receivers designed for high-speed optical short-reach transmission links.

Silicon Photonic Carrier-Assisted Differential Detection Receiver With High Electrical Spectral Efficiency for Short-Reach Interconnects

Coherent detection is advantageous in achieving high electrical spectral efficiency (ESE) relative to direct detection (DD), due to its capability of field recovery. However, the stringent requirement on the laser sources prevents it from being widely utilized in cost-sensitive short-reach applications. Carrier-assisted differential detection (CADD) was proposed to retrieve the optical field without needing for a narrow-linewidth local oscillator (LO) in a receiver. To realize a compact CADD receiver, silicon photonic (SiP) integration is therefore of particular interest since it leverages the standard complementary metal-oxide semiconductor (CMOS) compatible fabrication, offering high yield, low cost, and compact footprint. The fabrication process does not introduce III-V materials as the CADD receiver is LO-free. In this article, we fabricated a SiP integrated CADD receiver and demonstrated the transmission and reception of a 240-Gb/s orthogonal frequency division multiplexing (OFDM) 16-ary quadrature amplitude modulation (16-QAM) signal transmitted over an 80-km single-mode fiber (SMF) link, with a bit error ratio (BER) below the 25% overhead (OH) soft-decision forward error correction (SD-FEC) threshold. To the best of our knowledge, we achieve a record 5.2-b/s/Hz ESE per polarization for an integrated DD receiver.

Analytical Study and Noise Mitigation for Complex-Valued Optical DSB Transmission With Carrier-Assisted Differential Detection Receiver

A thorough analysis of the system model for complex-valued optical double-sideband (DSB) transmission with carrier-assisted differential detection (CADD) receiver under the influence of laser phase noise and fiber chromatic dispersion (CD) is presented. It is shown that the interaction of laser phase noise and CD leads to the phenomenon of phase-to-amplitude (P2A) noise and equalization-enhanced phase noise (EEPN). The achievable performance of the complex-valued optical DSB transmission with CADD receiver under the influence of EEPN and P2A noise is estimated by a closed-form expression, and it is verified by simulation that the results show an inaccuracy of less than 1 dB for a wide range of system parameters. In addition, in order to mitigate the EEPN and P2A noise, we propose a pre-decision aid-based simplified blind phase search (BPS) algorithm, commonly referred to as PDA-BPS algorithm. The PDA-BPS algorithm allows for reduced complexity by decreasing the number of symbols entering the BPS algorithm. Theoretical derivation and simulation verification illustrate that the PDA-BPS algorithm can achieve similar mitigation performance to the BPS algorithm with lower complexity. Specifically, under the condition that classification decision threshold R is equal to 0.25, the complexity can be reduced by 40%/16.6% with 1 MHz/7 MHz linewidth for 16-QAM and 29%/10.9% with 0.5 MHz/3 MHz linewidth for 64-QAM.

On Multi-User Deep-Learning-Based Non-Coherent DPSK Multiple-Symbol Differential Detection in Massive MIMO Systems

In view of reducing the complexity of signal detection in massive multiple-input multiple-output (MIMO) receivers, the use of non-coherent detection is favored over usual coherent techniques that require complex channel estimation. In this paper, a deep-learning approach to implement non-coherent multiple-symbol detection for differential phase-shift keying (DPSK) multi-user massive MIMO systems is proposed. The proposed deep-learning implementation reduces the high computational complexity required in conventional DPSK detection techniques. Two deep-learning-based multiple-symbol differential detection receiver designs are proposed and compared with decision-feedback differential detection (DFDD), and conventional multiple-symbol differential detection (MSDD) for the same system parameters. Multiple-symbol differential sphere detection (MSDSD) is used to implement conventional MSDD. The results show that the proposed deep-learning-based multiple-symbol differential detection implementation outperforms decision-feedback differential detection and achieves an optimal performance compared to conventional multiple-symbol differential detection implemented by multiple-symbol differential sphere detection for single-user and multi-user scenarios.

Symmetric carrier assisted differential detection receiver with low-complexity signal-signal beating interference mitigation.

Low-cost, spectrally efficient self-coherent detection capable of optical field recovery is desired for inter-data center connections and metro networks. In this work, a simplified symmetric carrier assisted differential detection (S-CADD) receiver structure is proposed, which removes the single-ended photodiode branch and saves one ADC in standard asymmetric CADD (A-CADD) receivers. To compensate for the signal-signal beating (SSBI) impairment, a low-complexity iterative SSBI mitigation algorithm is put forward as well. The computational complexity is reduced by moving equalization, de-modulation and modulation out of each iteration. Based on single-carrier twin-single sideband (SSB) pulse- and quadrature-amplitude modulation (PAM and QAM) signals, the OSNR sensitivity with different carrier-to-signal power ratios (CSPRs) at back-to-back (BTB) scenario, the bit-error rates (BER) performance after 1000km fiber transmission, and the received optical power sensitivity at BTB are theoretically and numerically compared for both S-CADD and A-CADD receivers, respectively.

Differentially-Keyed IR-UWB Signals for MA with Differential-Detection Receiver

Noncoherent communication receivers (differential-detectors) have simple design, however, they always incur bit error rate (BER) performance loss up to 3dB compared to coherent receivers. In this paper, a differential-detector is proposed for impulse radio ultra wideband (IR-UWB) communication systems. The system employs bit-level differential phase shift keying (DPSK) combined with code division (CD) for IR-UWB signals to support multiple-access (MA). It is analyzed under additive white Gaussian noise (AWGN) corrupted by multiple-access interference (MAI) channel. Its BER performance is compared against a reference coherent receiver using Monte-Carlo simulation method. A closed form expression for its average probability of error is derived analytically. Simulation results and theoretical analysis confirm the applicability of the proposed differential-detector for IR-UWB communication systems.

Differential detection of DPSK with frequency offset compensation

A baseband differential-detection receiver for DPSK, incorporating a planar extended Kalman filter for Doppler frequency offset estimation and compensation, is presented. Simulations show that its performance is close to the ideal case of no frequency offset. It is ideal for digital implementation and finds applications in mobile radio communications.