Yu-Sheng Liao

Long-Cavity Fabry–Perot Laser Amplifier Transmitter With Enhanced Injection-Locking Bandwidth for WDM-PON Application

We simulate the injection-locking performance of a 1% antireflection coated Fabry-Perot laser amplifier (AR-FPLA) and demonstrate the 2.5-Gbit/s DWDM-PON application with the directly modulated AR-FPLA based ONU transmitter under side-mode injection-locking condition. The effect of the AR-FPLA front-facet reflectivity on the injection locking range detuning and the Q-factor are interpreted from theoretical simulations and are experimentally characterized. A 25-channel locking capacity is reported for such a side-mode injection-locked AR-FPLA with corresponding wavelength locking range of 30 nm, the minimal requested power of -7 dBm and gain extinction ratio of <;7 dB by reducing its front-facet reflectivity to 1%. At bit rate of 2.5 Gbit/s, the BER of 10-12 is achievable for the nearest 17 channels of AR-FPLA at receiving power of -21 dBm, and all of the 25 injection-locked channels with SMSR of > 35 dB can guarantee the BER of <; 10-9 with their worst receiving sensitivity degrading to -19 dBm.

Dynamics of optical backward-injection-induced gain-depletion modulation and mode locking in semiconductor optical amplifier fiber lasers

The optical gain-depletion-induced mode-locking dynamics of a semiconductor optical-amplifier-based fiber ring laser (SOAFL) backward injected by a purely sinusoidally modulated or digitally encoded distributedfeedback laser diode are theoretically and experimentally demonstrated. The effect of gain depletion and waveform on the mode-locked pulse width, pulse shape, and power of the SOAFL are interpreted from theoretical simulations. The shortest pulse width of 12 ps can be generated from an optically sinusoidal-wave-modulated SOAFL. By backward injecting the SOAFL with a digitally encoded optical signal of adjustable duty cycle, one can observe the optimized gain depletion time of 400-600 ps required for mode locking the SOAFL.

L-band Erbium-doped fiber laser with coupling-ratio controlled wavelength tunability

By controlling the output coupling ratio, we demonstrate a novel wavelength-tunable L-band Erbium-doped fiber laser (EDFL) with a maximum tuning range up to 58 nm (from 1567 to 1625 nm) by controlling its output coupling ratio between 1% and 99%. The L-band EDFL is configured by using a bi-directionally dual-wavelength pumped EDFA in close-loop with an output coupler of tunable coupling ratio and an air-gap inserted FC/PC connector pair. Such an EDFL exhibits a quantum efficiency of 42% and an ultra-high power conversion efficiency of 37% under optimized pumping scheme, providing the small-signal gain and output power of ~34 dB and 91 mW, respectively. Low variation of <1.2 dB on channel power, power fluctuation of 0.04% and a narrow linewidth of 0.03 nm are obtained.

Side-mode transmission diagnosis of a multichannel selectable injection-locked Fabry-Perot Laser Diode with anti-reflection coated front facet

Theory and experiments on the side-mode-suppression-ratio (SMSR) enhancement and the linewidth reduction of a Fabry-Perot laser diode (FPLD) side-mode-injection-locked by using another FPLD are demonstrated to realize its potential application as a DWDM transmitter source. The SMSR, the spectral linewidth and the linewidth enhancement factor are simulated to realize the limitation of the FPLD-FPLD link under side-mode injection-locking condition. A degradation of the linewidth enhancement factor from 1.5 to 2.1 is observed due to the slave FPLD injection-locked at principle- and side-mode conditions. Up to 22-channel selectability of the 2.5 Gbit/s directly modulated FPLD based transmitter under side-mode injection-locking is demonstrated with a SMSR >35 dB, a Q-factor 6.8-9.2, a locking range of 24 nm, a power penalty of -0.7 dB, and a BER of 10(-10) at -17 dBm. The side-mode injection-locked FPLD shows high-quality transmission performance and meet the demand for cost-effective and high-capability 2.5 Gbit/s WDM systems.

The detuning characteristics of rational harmonic mode-locked semiconductor optical amplifier fiber-ring laser using backward optical sinusoidal-wave injection modulation

The modulation waveform, power, and frequency detuning dynamics of a semiconductor optical amplifier fiber-ring laser (SOAFL) harmonic and rational-harmonic mode-locked by using backward injection of a large-signal sinusoidal-wave modulated Fabry-Pe/spl acute/rot laser diode (FPLD) are studied. The shortest pulsewidth of 53.3 ps at 1 GHz with spectral linewidth of 0.09 nm at modulation power of 17 dBm can be obtained, which corresponds to a time-bandwidth product of 2.8. The threshold modulation power and the maximum frequency detuning range for harmonic mode-locking of the SOAFL are 11.5 dBm and 180 kHz, respectively. The mode-locked SOAFL gradually recovers back to sinusoidal-wave modulation mode at the detuning frequency beyond /spl plusmn/400 kHz. The pulse broadening slopes for the positive- and negative-frequency detuning regions of 0.48 and 0.375 ps/kHz are determined, respectively. By enlarging the modulating power and detuning the modulation frequency of FPLD, the SOAFL can be rational-harmonic mode-locked up to 12 GHz with 33-ps pulsewidth.

A pulsated weak-resonant-cavity laser diode with transient wavelength scanning and tracking for injection-locked RZ transmission

By spectrally slicing a single longitudinal-mode from a master weak-resonant-cavity Fabry-Perot laser diode with transient wavelength scanning and tracking functions, the broadened self-injection-locking of a slave weak-resonant-cavity Fabry-Perot laser diode is demonstrated to achieve bi-directional transmission in a 200-GHz array-waveguide-grating channelized dense-wavelength-division-multiplexing passive optical network system. Both the down- and up-stream slave weak-resonant-cavity Fabry-Perot laser diodes are non-return-to-zero modulated below threshold and coherently injection-locked to deliver the pulsed carrier for 25-km bi-directional 2.5 Gbits/s return-to-zero transmission. The master weak-resonant-cavity Fabry-Perot laser diode is gain-switched at near threshold condition and delivers an optical coherent pulse-train with its mode linewidth broadened from 0.2 to 0.8 nm by transient wavelength scanning, which facilitates the broadband injection-locking of the slave weak-resonant-cavity Fabry-Perot laser diodes with a threshold current reducing by 10 mA. Such a transient wavelength scanning induced spectral broadening greatly releases the limitation on wavelength injection-locking range required for the slave weak-resonant-cavity Fabry-Perot laser diode. The theoretical modeling and numerical simulation on the wavelength scanning and tracking effects of the master and slave weak-resonant-cavity Fabry-Perot laser diodes are performed. The receiving power sensitivity for back-to-back transmission at bit-error-rate <10(-10) is -25.6 dBm, and the power penalty added after 25-km transmission is less than 2 dB for all 16 channels.

All-Optical Decision-Gating of 10-Gb/s RZ Data in a Semiconductor Optical Amplifier Temporally Gain-Shaped With Dark-Optical-Comb

We demonstrate a novel all-optical noninverted OC-192 return-to-zero (RZ) decision-gate by using a semiconductor optical amplifier (SOA) which is gain-controlled to achieve an extremely high cross-gain-modulation depth and a narrow gain window. A dark-optical-comb generated by reshaping the optical clock RZ data in a Mach-Zehnder intensity modulator is employed as an injecting source to temporally deplete most of the gain in the SOA. Such a dark-optical-comb injected SOA decision-gate exhibits improved 3R regeneration performances such as a timing tolerance of 33.5 ps, Q -factor of 8.1, an input dynamical tolerance of 14 dB, and an extinction ratio (ER) of 14 dB. The deviation between the wavelengths of backward injected dark-optical-comb and input RZ data for optimizing the ER of the decision-gate is determined as Deltalambda=19 nm. Under a threshold operating dark-optical-comb power of 7 dBm, such a decision-gate can recover the -18.5-dBm degraded RZ data with a bit-error-rate of less than at 10-9 Gb/s. A negative power penalty of -4.2 dB is demonstrated for the RZ data after 50-km propagation and decision gating.

Harmonic Injection-Locking Behavior of Frequency-Detuned Optical Pulse in Erbium-Doped Fiber Laser

The harmonic injection-locking dynamics of a gain-switched laser diode (GSLD) pulse-injection-locked Erbium-doped fiber amplifier-based laser (EDFL) are studied. Under GSLD injection with a pulsewidth and an average power of 17.6 ps and 0.2 mW, respectively, at a repetition frequency corresponding to the 223rd harmonic (996.8635971 MHz) of the EDFL, the pulsewidth, peak power, and phase noise of the injection-locked EDFL are broadening from 34.3 ps to 130 ps, decreasing from 1.8 W to 500 mW, and increasing from -101.5 dBc/Hz to -86 dBc/Hz, respectively, as the repetition frequency detunes toward the injection-locking margin. The injection-locking range is from -13 kHz to +27 kHz. The peak power of the broadened pulses is greatly reduced to one third of that at the zero-detuning condition even with a detuning frequency of ±5 kHz. The injection-locked EDFL pulse-train eventually disappears as the repetition frequency of the GSLD detuned beyond the injection-locking bandwidth. The timing jitter of the GSLD harmonic injection-locked EDFL remains unchanged (<0.5 ps) within a positive detuning frequency of <25 kHz, which is less stable at a negatively frequency-detuned regime.

Pulsating master and injected slave weak-resonant-cavity laser diodes based quasi-color-free 2.5Gb/s RZ DWDM-PON

The 25-km bi-directional 2.5Gb/s pulsed-RZ transmission in a quasi-color-free DWDM-PON with down- and up-stream slave weak-resonant-cavity Fabry-Perot laser diodes (WRC-FPLDs) coherently injection-locking and pulsating by a gain-switched master WRC-FPLD after 200-GHz AWG channelization is demonstrated.

In Situ and Self-Restorable Injection-Locking Monitor by Integrated Photodiode for FPLD WDM Transmitter

A novel in situ self-restoration scheme to track real time the injection locking of a Fabry-Perot laser diode (FPLD) is demonstrated by a built-in integrated monitor photodiode (MPD). The variation in the received photocurrent of the integrated MPD was calculated by a microcontroller unit integrated with an analog-to-digital converter, which is employed to dynamically control the temperature of the FPLD via a thermal-electrical controller for wavelength stabilization. Such a scheme can be effectively implemented with a minimum amount of redundant network resources to achieve self-restoration within 50 s with Q factor >;8.2 and side-mode suppression ratio >;35 dB at 2.5 Gbit/s. The feasibility of the proposed self-restorable locker is suitable for most wavelength-locking FPLDs within high-speed wavelength-division multiplexing networks.