Alexandre Shen

Experimental investigation of the timing jitter in self-pulsating quantum-dash lasers operating at 1.55 µm

We report for the first time on the systematic measurement of timing jitter of 40-GHz self-pulsating Fabry-Perot laser based on InAs/InP quantum dashes emitting at 1.55 microm. Two different methods, one based on optical cross-correlation and one on electrical spectrum sideband integration are used and show a good agreement, yielding a jitter of 0.86 ps in the 1 MHz---20 MHz frequency range with a potential of 280 fs for optimized driving conditions. Amplitude noise and high-frequency timing jitter contributions are also discussed.

Quantum-Dash Mode-Locked Laser as a Source for 56-Gb/s DQPSK Modulation in WDM Multicast Applications

We investigate wavelength tunable 56-Gb/s differential quaternary phase-shift keying (DQPSK) systems using comb generation in a quantum-dash mode-locked laser for wavelength-division-multiple access (WDM)-based broadcast application. We present relative intensity noise and bit-error-rate measurements for each mode. We demonstrate error-free operation over nine WDM channels with 100-GHz spacing.

Separate Error-Free Transmission of Eight Channels at 10 Gb/s Using Comb Generation in a Quantum-Dash-Based Mode-Locked Laser

We report on comb generation at 1.55 mum using a mode-locked quantum-dash-based laser. A flat optical spectrum with a ~10-nm width consisting of eight 100-GHz-spaced channels is demonstrated. Separate error-free transmission of each channel is achieved at 10 Gb/s over 50-km-long single-mode fiber. Compared to an ideal external cavity continuous-wave laser, a penalty of only 1.5 dB is measured for each filtered channel. This is attributed to the higher relative intensity noise level of a filtered mode.

Multi-Data-Rate System Performance of a 40-GHz All-Optical Clock Recovery Based on a Quantum-Dot Fabry–PÉrot Laser

Bit-error-rate assessment of a multi-rate all-optical clock recovery (OCR) based on a narrow linewidth mode-locked quantum-dot (QD) Fabry-Perot laser is presented in this letter. OCR has been achieved without external feedback. We use a QD Fabry-Perot semiconductor laser designed for 40-GHz clock extraction. We then present OCR performance with 40-, 80-, and 160-Gb/s input data signal and demonstrate that clock recovery has been obtained thanks to subharmonic locking process. Results are presented through penalty measurement using an original characterization based on recovered clock remodulation with electrical data from the transmitter. This technique allows us to evaluate the quality of the recovered clock.

Analysis of thermal limitations in high-speed microcavity saturable absorber all-optical switching gates

The limitations owing to device heating and thermo-optic effects in high-speed quantum-well microcavity saturable absorber devices are investigated both theoretically and experimentally. A simplified theoretical description of the device electronic, thermal, and optical properties is developed and applied to the modeling of the device switching characteristics for reamplification + reshaping step (2R) all-optical regeneration. These predictions are compared to nonlinear optical measurements performed with switching pulses of fixed duration and variable repetition rate on two devices with significantly different thermal properties. It is shown that proper optimization of the device thermal properties is crucial to avoid the degradation of device performance at high bit rate. It is also shown that the negative effects of optically induced heating on the switching contrast may be compensated to some extent by operating the device on the long wavelength side of the microcavity resonance

Error-free transmission of 8 WDM channels at 10 Gbit/s using comb generation in a quantum dash based mode-locked laser

Error-free transmission over 50 km single mode fiber of 8 WDM ITU channels with 100 GHz channel spacing is demonstrated at 10 Gbit/s by using comb generation in a quantum dash mode-locked laser.

Cascadability assessment of a 2R regenerator based on a saturable absorber and a semiconductor optical amplifier in a path switchable recirculating loop

We assess a new 2R regenerator based on a microcavity saturable absorber and a semiconductor optical amplifier. Cascadability is demonstrated and the impact of regeneration span is studied in a 10-Gb/s two-path recirculating loop. A wavelength study demonstrates the tunability of the device over 13 nm

A Vision for Thermally Integrated Photonics Systems

Thermal management has traditionally been relegated to the last step in the design process. However, with the exponential growth in data traffic leading to ever-greater levels of component integration and ever-higher levels of energy consumption, thermal management is rapidly becoming one of the most critical areas of research within the ICT industry. Given the vast use of optics for efficient transmission of high-speed data, this paper focuses on a new thermal solution for cooling the components within pluggable optical modules. Thermally Integrated Photonics Systems (TIPS) represents a new vision for the thermal building blocks required to enable exponential traffic growth in the global telecommunications network. In the TIPS program, existing thermal solutions cannot scale to meet the needs of exponential growth in data traffic. The main barriers to enabling further growth were identified and a research roadmap was developed around a scalable and efficient integrated thermal solution. In particular, the effects of replacing inefficient materials and large macroTECs with better thermal spreaders and μTECs are investidated. In addition, new forms of μChannel cooling into the package to more efficiently remove the heat generated by the lasers and the TECs are being studied which can lead to future photonic devices that can be deployed in a vastly more dense and integrated manner to address the requirements of future telecommunication networks.

Bidirectional 2.5-Gb/s WDM-PON Using FP-LDs Wavelength-Locked by a Multiple-Wavelength Seeding Source Based on a Mode-Locked Laser

We experimentally investigate the operation of a cost-effective wavelength-division-multiplexed passive optical network (WDM-PON) based on wavelength-locked Fabry-Pérot laser diodes (FP-LDs). A single quantum-dash passively mode-locked laser (QD-MLL) is combined with an arrayed waveguide grating in WDM-PON architecture to provide a low-noise, coherent multiwavelength seeding source to injection-lock the FP-LDs for both downstream and upstream. The results show that the QD-MLL-injected FP-LD has the same performance when compared to the case of injection-locking by a low-noise external cavity laser. Error-free bidirectional transmission over 25 km for 16 channels with 42.7-GHz channel spacing is demonstrated at 2.5 Gb/s in the C -band and an optical budget higher than 30 dB is reached.

Low-timing-jitter all-optical clock recovery for 40 Gbits/s RZ-DPSK and NRZ-DPSK signals using a passively mode-locked quantum-dot Fabry–Perot semiconductor laser

We investigate experimentally all-optical clock recovery for return-to-zero (RZ) and nonreturn-to-zero (NRZ) differential phase-shift keying (DPSK) signals at 40 Gbits/s using a passively mode-locked quantum-dot Fabry-Perot (QD-FP) semiconductor laser. The QD-FP laser exhibits a beat spectrum linewidth of 80 kHz, which enables a recovered clock signal with a root-mean-square timing jitter of 160 fs for the RZ-DPSK signal and 240 fs for the NRZ-DPSK signal. The timing jitter of the recovered clock signal is characterized for different values of the input signal power and the input signal optical signal-to-noise ratio.