Zhenguo Lu

Arrayed-waveguide-grating-based interrogator for wavelength-modulated multi-fiber-optic sensor applications

Simultaneous interrogation of six distributed wavelength modulated fiber-optic sensors has been demonstrated using an arrayed-waveguide-grating-based interrogation technique proposed by our laboratory. This letter analyzes the operating principle of the method and reports the experimental results of this application. The results show that the interrogator proposed offers better than 1-pm wavelength resolution and has the potential of being packaged into a hand-held rugged device.

A

A passive InAs/InP quantum dot (QD) semiconductor mode-locked laser (MLL) emitting 403-GHz repetition rate pulses with 268- and 563-fs pulse durations is demonstrated experimentally around 1.54 μm. The QD MLL consists of a QD Fabry-Pérot laser and external cavities that include eight fiber Bragg gratings (FBGs). The mode-locking is realized by four-wave mixing in the QD waveguide between the longitudinal modes selected by the FBGs.

C

A multiwavelength laser with maximum signal-to-noise ratio up to 62 dB was demonstrated on the basis of a 461-m-long InAs-InGaAsP quantum-dot waveguide Fabry-Perot cavity chip. It has 24 channels with 0.8-nm channel spacing and 8.0-dB maximum channel intensity nonuniformity over a wavelength range from 1612 to 1632 nm. Its channel spacing irregularity due to linear intracavity waveguide dispersion was also investigated.

-Band InAs/InP Quantum Dot Semiconductor Mode-Locked Laser Emitting 403-GHz Repetition Rate Pulses

This report presents an investigation of composite fiber Raman amplifiers (i.e., a distributed fiber Raman amplifier followed by a discrete fiber Raman amplifier) with in-coherent pumping, compared to conventional coherent pumping. It is shown that a flatter gain, noise figure and optical signal-to-noise ratio (OSNR) over 100-nm bandwidth can be achieved simultaneously by using two counter-incoherent pumps, compared to using six counter-coherent pumps. Moreover, it is found that a further improvement in gain, noise figure and OSNR flatness can be obtained in composite fiber Raman amplifiers with bi-directional incoherent pumping. The flatness of both gain and OSNR with a ripple of 1 dB is predicted by using one co-incoherent pump and one counter-incoherent pump.

1.6-

A short pulse train with pulsewidth was generated in a quantum dot mode-locked laser (QD MLL). Due to the short dispersion length, it is required to include group-velocity dispersion (GVD) in modeling pulse train generation and evolution from QD MLLs. On the other hand, Kerr effect is also required to consider due to high peak power density in the laser cavity, and its induced self-phase modulation (SPM) also contributes to the pulse evolution. In this paper, a time domain traveling wave model, including the effect of GVD and SPM, combined with rate equations, is established to model the pulse evolution in a single-section QD MLL. It is shown that the pulse evolution calculated by this model is in reasonable agreement with the experiments. The contribution to the pulse evolution by the GVD and SPM impact is discussed.

\mu

Tunable terahertz beat signal generation is demonstrated by using a C-band InAs/InP quantum-dot (QD) mode-locked laser combined with external cavity of two fiber Bragg gratings (FBGs), where one of the FBGs is tunable in wavelength. Beat signals with ultra-high repetition rates quasi-continuously from 1 to 2.21 THz are observed between the two modes, which are phase-correlated due to intracavity four-wave mixing effect in the QD waveguide.

m Multiwavelength Emission of an InAs–InGaAsP Quantum-Dot Laser

Optical fiber sensors have shown great potentials for aerospace applications. But two issues need to be addressed before these applications can be realized. One is how to reliably implement optical sensors in the air vehicles. The other is the need of compact, low weight sensor interrogation systems. We propose to use planar lightwave circuits (PLC) to address the second issue. In this article, we report some of our results on the development of both echelle diffractive gratings based sensor interrogator and arrayed waveguide gratings based sensor interrogators. Both approaches offer miniaturized solutions for the development of optical fiber sensor interrogation systems.

Composite broad-band fiber Raman amplifiers using incoherent pumping.

A novel optical signal-to-noise ratio (OSNR) monitor has been proposed and demonstrated. The device is completely passive, very simple, compact and cost effective. More than 30 dB dynamic range polarization insensitive OSNR monitoring has been achieved.

Modeling of Single-Section Quantum Dot Mode-Locked Lasers: Impact of Group Velocity Dispersion and Self Phase Modulation

Current communication networks needs to keep up with the exponential growth of today’s internet traffic, and telecommunications industry is looking for radically new integrated photonics components for new generation optical networks. We at National Research Council (NRC) Canada have successfully developed nanostructure InAs/InP quantum dot (QD) coherence comb lasers (CCLs) around 1.55 m. Unlike uniform semiconductor layers in most telecommunication lasers, in these QD CCLs light is emitted and amplified by millions of semiconductor QDs less than 60 nm in diameter. Each QD acts like an isolated light source acting independently of its neighbours, and each QD emits light at its own unique wavelength. The end result is a QD CCL is more stable and has ultra-low timing jitter. But most importantly, a single QD CCL can simultaneously produce 50 or more separate laser beams at distinct wavelengths over the telecommunications C-band. Utilizing those unique properties we have put considerable effort well to design, grow and fabricate InAs/InP QD gain materials. After our integrated packaging and using electrical feedback-loop control systems, we have successfully demonstrated ultra-low intensity and phase noise, frequency-stabilized integrated QD CCLs with the repetition rates from 10 GHz to 100 GHz and the total output power up to 60 mW at room temperature. We have investigated their relative intensity noises, phase noises, RF beating signals and other performance of both filtered individual channel and the whole CCLs. Those highly phase-coherence comb lasers are the promising candidates for flexible bandwidth terabit coherent optical networks and signal processing applications.

Tunable Terahertz Beat Signal Generation From an InAs/InP Quantum-Dot Mode-Locked Laser Combined With External-Cavity

We present the application of metal-dielectric coatings on the facet of waveguides for the control of the modal reflectance with narrowband and wideband mirrors.