Jifang Qiu

All-Optical Logic Gate for XOR Operation Between 40-Gbaud QPSK Tributaries in an Ultra-Short Silicon Nanowire

We demonstrate an all-optical XOR logic gate for 40-Gbaud quadrature phase-shift keying (QPSK) tributaries in a silicon nanowire for the first time. The XOR logic operation is realized based on four-wave mixing (FWM) in the C-band. Experimental results show negligible power penalty at a bit error ratio (BER) of 10-6 compared with the back-to-back signals. The BER floor appears at BER of 10-6 for both I and Q tributaries of the logic operation, and the main reasons are the optical signal-to-noise ratio (OSNR) deterioration caused by nonlinear loss due to free carrier absorption (FCA) and two-photon absorption (TPA) and the cross-phase modulation (XPM)-induced phase impairments.

Multi-wavelength in-band OSNR monitor based on Lyot-Sagnac interferometer

An in-band OSNR monitor based on Lyot-Sagnac interferometer is experimentally demonstrated for 4×40GBaud NRZ-QPSK WDM signal without requirement for prior knowledge of the noise-free coherence properties of the signal. OSNR from 7.5~25dB was realized.

Integrated In-Band OSNR Monitor Based on Asymmetrical Parallel-MZIs for WDM signals

We propose a novel in-band optical signal-to-noise ratio (OSNR) monitor based on asymmetrical parallel Mach-Zehnder interferometers (A-PMZI). By exploiting two different lengths of delay arms in the A-PMZI, the monitor requires no prior knowledge of the noise-free coherence properties of the signal. The A-PMZI is fabricated on a SOI platform and demonstrated for OSNR monitoring of 4 × 28 GBd NRZ-QPSK WDM signals. Experimental results show that OSNR measurements from 7.7 to 24.8 dB within error of ±0.5 dB are achieved for all four channels. Due to the advantages of high fabrication tolerance and broad bandwidth of multimode interferometer couplers in the A-PMZI, the monitor works well in the whole C-band. Moreover, the monitor is insensitive to input optical power and chromatic dispersion.

Generation of Nyquist Pulses Using a Dual Parallel Mach-Zehnder Modulator

We demonstrated the generation of Nyquist pulses using a dual parallel Mach-Zehnder modulator. 10 GHz to 40 GHz Nyquist pulses with timing-jitter below 258 fs and signal-to-noise ratio more than 30 dB are experimentally generated.

Low timing jitter 40 Gb/s all-optical clock recovery based on an amplified feedback laser diode

We demonstrate 40 Gb/s all-optical clock recovery by using a monolithic integrated amplified-feedback laser (AFL) with coherent injection-locked method. The AFL consists of a gain-coupled DFB laser and an optical amplified feedback external cavity. With proper design and operation of AFL, the device can work at self-pulsation state that resulted from the beating between two lasing modes. The self-pulsation can be injection-locked to the optical clock embedded in input data streams. Due to different work mechanisms, there are two all-optical clock recovery operation modes: incoherent injection-locked and coherent injection-locked. Its predicted that the coherent injection method has various advantages: 1) requiring low injection power recovery, 2) independent of the bit rate and 3) introducing little timing jitter to the recovered clock. The robustness of coherent clock recovery is confirmed by our experimental results. We set up a return-to- zero (RZ) pseudorandom binary sequence (PRBS) data streams all-optical clock recovery system. This coherent injection-locked based clock recovery method is optical signal noise ratio (OSNR) and chromatic dispersion (CD) degeneration tolerant, and has low timing jitter and high sensitivity.

A wavelength-insensitive 2nd-order mode generator with Multimode Interference waveguides and a phase shifter

We propose a novel high-performance mode convertor based on Multimode Interference waveguides, which can convert the fundamental mode (TE0) to the second-order mode (TE2). Simulation results show that the device is wavelength insensitive and has excellent fabrication tolerance.

Tunable multi-wavelength dissipative soliton generation in an Yb-doped fiber laser based on SESAM and Lyot-Sagnac filter

Tunable multi-wavelength dissipative solitons (DSs) were experimentally demonstrated in an Yb-doped fiber laser based on semiconductor saturable absorption mirror (SESAM) and Lyot-Sagnac filter. Thanks to the tunability of the Lyot-Sagnac filter, mode locking of up-to-6-wavelength DSs was achieved.

160 Gbaud single nyquist channel transmission through emulated 4 km free-space turbulence link

A single 160 Gbaud Nyquist channel transmission based on coherent matched sampling under 4 km lab-emulated free-space turbulence link is demonstrated. Turbulence induced power fluctuation is found to be main reason of performance deterioration.

A novel wavelength multiplexer/demutiplexer based on side-port multimode interference coupler

Based on side-port multimode interference coupler, a novel design of 1.31/1.55-μm wavelength multiplexer/demutiplexer on SOI platform with conventional channel waveguides is proposed and analyzed by using wide-angle beam propagation method. With a 25.9μm long ultra-short MMI section, nearly an order of magnitude shorter than that of the previously reported 1.31/1.55-μm wavelength MMI splitters on SOI, simulation results exhibit contrasts of 28dB and 25dB at wavelength 1.31 and 1.55 μm, respectively, and the insertion losses are both below 0.55dB. Meanwhile, the analysis shows that the proposed structure has larger fabrication tolerances than restricted MMI based structures and the present design methodology also applies to split other wavelengths and in different material platforms, such as InP, GaAs and PLC guides, etc.

On-chip integratable all-optical quantizer using cascaded step-size MMI

We propose a novel all-optical phase shifted quantizer using cascade step-size MMI. The operation principle has been derived in detail. A 3-bit quantizer and a 5-bit quantizer are designed and simulated based on 220-nm SOI platform to verify the feasibility of the scheme, of which the lengths are all below 200 μm. To the best of our knowledge, they have the most compact footprint compared to the existing all-optical quantizers. In the end, the fabrication error analyses of the proposed quantizers are carried out to verify their stability.