Coherent Burst-mode Receiver Research Articles

7424 × 7424 Optical Circuit Switch With 1.4 μs Switching Time Enabled by Silicon-Photonic 64-Port Space Switches and Burst-Mode Coherent Receivers

7424 × 7424 Optical Circuit Switch With 1.4 μs Switching Time Enabled by Silicon-Photonic 64-Port Space Switches and Burst-Mode Coherent Receivers

Fast Feed-Forward Optical and Electrical Gain Control to Extend the Dynamic Range of the Burst-Mode Digital Coherent Receiver for High-Speed TDM-PON Systems

This paper introduces a new burst-mode coherent receiver configuration that drastically widens the receiver input dynamic range. Its key advance is a fast feed forward gain control scheme for both a semiconductor optical amplifier (SOA) used as a preamplifier and trans-impedance amplifiers (TIAs) set at the coherent receiver. The two-stage optical and electrical gain control greatly decreases the received burst signal's power variations and increases the receiver dynamic range which attenuates the quantization errors in analogue-to-digital conversion (ADC). To elucidate the receiver sensitivity characteristics, bit error rate (BER) calculations are conducted on 10 Gbit/s single polarization quadrature phase shift keying (SP-QPSK) signal coherent reception. The calculations focus on two significant parameters that greatly impact the quantization noise; ADC vertical resolution and received signal's state of polarization (SOP). The calculation results confirm that the proposed configuration achieves high sensitivity, better than −44 dBm, and wide dynamic range of 30 dB in the worst SOP condition, even when 5-bit ADC is used. Transmission experiments verify the calculated sensitivities and extremely high loss budget of 48.6 dB is achieved in 40-km single mode fiber (SMF) transmission. These results show that the proposal has the potential to realize 10 Gbit/s class long-reach and high splitting ratio PONs; the extremely wide dynamic range yields 40 km reach PON systems with 512- or 1024-way splits with no change in receiver configuration.

Demonstration of Real-Time Burst-Mode Digital Coherent Reception With Wide Dynamic Range in DSP-Based PON Upstream

This paper proposes a real-time burst-mode coherent receiver (BMCR) that enables wide dynamic range reception for future passive optical network (PON) applications, wherein two key burst-mode components are implemented; an automatic gain controlled semiconductor optical amplifier (AGC-SOA) for optical power equalization and a real-time digital signal processor (DSP) with a frame detection (FD) function. The AGC-SOA greatly increases the receiver dynamic range by reducing the impact of quantization errors in the analogue-to-digital conversion used for DSP-based signal demodulation while the FD function detects burst frame arrivals for frame-by-frame optimization of tap weights of an adaptive filter in the DSP. Successful real-time reception of 20 Gb/s single polarization quadrature phase shift keying burst signals with wide dynamic range of 22.0 dB is experimentally demonstrated. New system configurations of the DSP-based coherent PONs using the BMCR and wavelength plans assigned to the new systems are also proposed to offer a smooth migration from existing PONs.

Ultra-High-Capacity Optical Packet Switching Networks with Coherent Polarization Division Multiplexing QPSK/16QAM Modulation Formats

Optical packet switching (OPS) networks and its subsystems, like the burst-mode receiver, are an essential technology currently used in passive optical networks (PONs). Moreover, OPS may play a fundamental role on future hybrid optical circuit switching (OCS)/OPS networks and datacenter networks. This paper focuses on two fundamental subsystems of packetized optical networks: the digital coherent burst-mode receiver and the electro-optical switch. We describe and experimentally characterize a novel digital coherent burst-mode receiver that makes uses of the Stokes parametrization to rapidly estimate the state of polarization (SOP) and optimize the equalizer convergence time. This burst-mode receiver is suitable for optical packetized networks that make use of advanced modulation formats such as quadrature amplitude modulation (QAM). We study the suitability of (Pb,La)(Zr,La)O3 (PLZT) optical switches for amplitude-variable coherent polarization division multiplexing (PDM) 16QAM modulation format and demonstrate a switching capacity of 10.24 Tb/s/port. We demonstrate a full 2 × 2 OPS node with a control plane capable of solving packet contention by means of packet dropping or buffering with a switching capacity of 10.24 Tb/s/port. Finally, we demonstrate the operation of the 2 × 2 OPS node with a record capacity of 12.8 Tb/s/port plus 100 km of dispersion-compensated fiber transmission.

Method of digital signal process aided by control signal for burst-mode coherent receivers

We propose a method of digital signal processing for a burst-mode coherent receiver, which can recover the burst data rapidly aided by a control signal. The feasibility and effectiveness of our proposed method are demonstrated in a 128 Gbps polarization division multiplexed quadrature phase shift keying modulation experiment, and the results show that the proposed method can reduce the 70% convergence time on average compared with the traditional digital signal processing without any training overhead or additional computing complexity.

High data rate coherent optical slot switched networks: a practical and technological perspective

We review several node architectures for optical slot switching ring networks, which can be used in metropolitan or datacenter applications, and compare them for their networking aspects. The dimensioning, quality of service, latency, and protection issues are discussed for the different approaches. The main devices, i.e. fast wavelength-tunable laser, burst-mode coherent receiver (which is required to enable high data rate transmission at 100 Gb/s and above), and a slot blocker for improved wavelength usage efficiency are described, and available technologies for each key building block are reviewed.

Optical coherent burst‐mode receivers with delayed channel equalisation feedback from parallel and pipelined design

A digital optical coherent burst-mode receiver (BMR) with 112-Gb/s polarisation-division multiplexing-quaternary phase-shift keying (QPSK) modulation is proposed with parallel digital signal processing and pipelined design. The convergence rate property of the digital channel equaliser with non-negligible computational delay is studied extensively using simulations. Owing to the interaction between the channel equalisation and frequency offset estimation (FOE), a novel equaliser adaptation method using the latest available equaliser output and the latest available FOE result is proposed for a faster convergence than the conventional method. Simulation results reveal that the computational delay have a great impact on the convergence rate. A smaller step size for tap coefficient updating with slower convergence rate should be used to avoid divergence. Compared with the FOE module, the computational delay from the channel equaliser has the dominant effect on the convergence. The design of the equaliser with short computational delay is the key for a fast convergence rate. The parallel and pipelined digital optical coherent BMR after successful initialisation has negligible error rate performance loss when compared with the ideal serial signal processing within a wide frequency offset range.

Fast-Tuning Coherent Burst-Mode Receiver for Metropolitan Networks

We demonstrate a fast wavelength-tunable burst-mode receiver for coherent 28 GBd dual-polarization quadrature phase shift keying signals using a commercially available DS-DBR laser as the local oscillator (LO). We find that the frequency drift and linewidth of the LO must be precisely controlled to prevent bit-error-ratio (BER) penalties when the signal undergoes transmission distances typical of metropolitan-area networks. We demonstrate reduction of the LO frequency drift and linewidth after wavelength switching by compensation using the phase section of the laser and achieve negligible BER penalty with burst-mode reception for single-mode fiber transmission up to 1280 km. We also measure the sensitivity of the receiver to LO detuning when multiple wavelength-division multiplexed channels are received simultaneously as in a broadcast-and-select network architecture.

Fast Wavelength Switching 6 GBd Dual Polarization 16QAM Digital Coherent Burst Mode Receiver

A commercially available digital supermode distributed Bragg reflector tunable laser is employed as a fast wavelength switching local oscillator (LO) in a dual polarization (DP) 16-quadrature amplitude modulation (16QAM) coherent burst mode receiver. A digital coherence enhancement technique is used to compensate both the Lorentzian and non-Lorentzian distributed phase noise of the tunable LO laser. It is shown that differential decoding is not sufficient to overcome the substantial bit errors caused by the LO laser phase noise. However, the coherence enhancement technique enables the reception of low symbol rate DP-16QAM bursts, with an average optical signal to noise ratio penalty of 3.5 dB observed relative to theory at the forward error correction threshold (1.5×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> ).

Wavelength tunable coherent burst-mode receiver design under transient frequency offset

Wavelength tunable optical coherent burst-mode receivers (BMR) can offer flexibility and sub-wavelength granularity for dynamic WDM networks. A new BMR design with dispersion equalizer plus frequency offset estimator is proposed for simultaneous dispersion compensation and frequency offset estimation. Its good performance is verified by simulations. A training sequence as short as 4 K symbols, corresponding to an initialization time of 160 ns, is found to be enough to support 200 km transmission distance plus over ± 5 GHz frequency offset. The new BMR design can also work under the case when transient frequency offset from wavelength tuning exists in the system.