Gordon Ning Liu

Beyond 100-Gb/s Transmission Over 80-km SMF Using Direct-Detection SSB-DMT at C-Band

For short-reach links, direct detection offers the advantages of low cost and low complexity. Discrete multitone (DMT) is a promising format due to its high spectral efficiency, flexibility and tolerance to chromatic dispersion (CD). In this study, we experimentally demonstrate a beyond 100-Gb/s DMT transmission over 80-km single mode fiber (SMF) without CD compensation. Using dual-drive Mach-Zehnder modulator-assisted single-sideband modulation, CD-induced power fading is eliminated after direct detection. Trellis coder modulation (TCM) is used to increase the Euclidean distance of the constellation points and nonlinearity equalization (NLE) is employed to mitigate system nonlinearities. Both TCM and NLE algorithms have contributions to improve the system performance. The experimental results show that high capacities up to 122, 110 and 105 Gb/s are achieved with bit error rate at 4.5 × 10-3 for back to back, 40- and 80-km SMF transmissions, respectively. The required OSNR after 80-km SMF transmission is 34.2 dB. To the best of our knowledge, this study reports the lowest required OSNR and highest capacity for C-band direct-detection transmission over 80-km SMF.

Advanced modulation formats for 400-Gbps short-reach optical inter-connection

Besides the long-haul optical networks covering over thousands of kilometers for backbone transmission, short reach optical networks (SR-ONs) are widely deployed in metro-area for aggregation and accessing. The SR-ONs include the metro optical transport networks (Metro-OTN), optical access networks or other optical inter-connection systems with even shorter distance. As predicted, the growing bandwidth demanding from SR-ONs will be much more than that from the long-haul optical networks in the near future. Besides, there are tremendous amounts of optical terminals and end-users in SR-ONs compared with the long-haul transmission systems and thus will induce large cost and huge energy consumption. So, the power and cost efficiency should be the key consideration for SR-ONs besides the transmission performance. To improve the power and cost efficiency in SR-ONs, advanced modulations and detection techniques based on low power, low cost and integrated optical modulators should be utilized. In this paper, different advanced modulation formats have been discussed. 56Gbps PAM4, 112Gbps poly-binary and 100Gbps DMT that can be used to realize 400-Gbps SR-ONs for different applications have also been demonstrated respectively. In addition, low-cost and low-power opto-electronic components suitable for SR-ONs, the impairments induced by all kinds of defects and bandwidth limitation of opto-electronic components and the corresponding compensation techniques based on DSP algorithms have also been discussed in the experiments.

112-Gbit/s × 4-lane duobinary-4-PAM for 400GBase

Novel duobinary-4-PAM signaling is experimentally demonstrated to support a 4-lane low-latency 400GbE client side solution. Direct detection of 112 Gbps transmission over a 5 km single wavelength and polarization fiber link is achieved.

C-band 56Gbps transmission over 80-km single mode fiber without chromatic dispersion compensation by using intensity-modulation direct-detection

C-band 56Gbps transmission over 80-km single mode fiber without chromatic dispersion compensation is realized by using discrete multi-tone modulation based on low cost electro-absorption modulated laser and receiver. The required OSNR of 26.3 dB at BER of 4E-3 is achieved.

Should like demands be grouped in mixed line rate networks

Grouping same line-rate channels makes no difference in growth-only networks, but significantly reduces fragmentation in dynamic networks and improves overall network throughput, particularly in congested operation scenarios.

112-Gb/s duobinary 4-PAM transmission over 200-m multi-mode fibre

We experimentally demonstrated an 850-nm VCSEL based 112-Gb/s short reach interconnection system with 200-m MMF transmission employing a duobinary 4-PAM format. The sensitivity of -4.8 dBm at the 6.7% overhead FEC limit (BER=4.2×10-4) was achieved.

OSNR Monitoring for Higher Order Modulation Formats Using Asynchronous Amplitude Histogram

We propose an asynchronous-amplitude-histogram-based optical signal-to-noise ratio monitoring technique for higher order modulation formats. Simulation results show that the proposed technique enables a wide monitoring range for 25-GSym/s nonreturn-to-zero/return-to-zero 16- and 64-quadrature amplitude modulation systems with high monitoring sensitivity. The tolerance of the monitoring technique to other signal impairments such as chromatic dispersion and polarization-mode dispersion is also investigated. The proposed technique can be used along transmission links with simple low-cost hardware and/or in digital signal processing (DSP)-based coherent receivers without additional hardware, thus enabling next-generation optical networks using higher order modulation formats to achieve transmission rates of 100 Gb/s per channel and beyond.

Ultra-compact contentionless ROADM architecture with high resilience based on flexible wavelength router

We present a novel CDC-ROADM architecture based on flexible wavelength router which consists of two N×N WSSs. The proposed architecture is compact, low cost and provides a fully 1+1 redundant solution with high resilience.

Regularized Sparse Recovery for Optical Power Monitoring With Low-Cost Tunable Optical Filters

We propose a regularized sparse recovery (RSR) technique to monitor optical power from the broadened optical spectrum acquired by scanning a tunable optical filter (TOF). The key idea of RSR is to find a smooth but sparse signal spectrum that matches the observed data of a broadened spectrum model within a tolerable error. Experiments demonstrated that RSR can be used to monitor accurately the power of mixed 10-G/40-G wavelength-division-multiplexing channels with 50-GHz channel spacing using commercial TOFs. This technique also has higher immunity to measurement and TOF response errors than the regularized least square method. It does not require strong repeatability of TOF response and makes the low-cost TOF suitable for optical power monitoring.

Low-loss and misalignment-tolerant fiber-to-chip edge coupler based on double-tip inverse tapers

A novel fiber-to-chip edge coupler with two tapered tips and a multimode interference combiner is demonstrated on a silicon-on-insulator platform. It has advantages over a single-tip edge coupler on coupling loss, bandwidth and misalignment tolerance.