Gong-Cheng Lin

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.

Comparison on Injection-Locked Fabry–Perot Laser Diode With Front-Facet Reflectivity of 1% and 30% for Optical Data Transmission in WDM-PON System

Externally amplified spontaneous emission (ASE) injection-locking characteristics and optical data transmission performances of a TO-56 can-packaged Fabry-Perot laser diode (FPLD) with 1% front-facet reflectivity are investigated using a wavelength-division-multiplexing passive-optical network (WDM-PON) system configured by an array-waveguide grating (AWG) based MUX/DMUX filters with channel spacing of 200 GHz. Quasi-single-mode output of such a nearly color-free weak-resonant-cavity FPLD with highest side-mode suppressing ratio of 31 dB is achieved with ASE injection-locking, providing a bit-error-rate (BER) of < 10-13 at receiving power of -31 dBm and a power penalty of 0.5 dB after 20-km transmission in single-mode fiber with a bit rate up to 1.25 Gbit/s.

200-GHz and 50-GHz AWG channelized linewidth dependent transmission of weak-resonant-cavity FPLD injection-locked by spectrally sliced ASE

In a weak-resonant-cavity Fabry-Perot laser diode (WRC-FPLD) based DWDM-PON system with an array-waveguide-grating (AWG) channelized amplified spontaneous emission (ASE) source located at remote node, we study the effect of AWG filter bandwidth on the transmission performances of the 1.25-Gbit/s directly modulated WRC-FPLD transmitter under the AWG channelized ASE injection-locking. With AWG filters of two different channel spacings at 50 and 200 GHz, several characteristic parameters such as interfered reflection, relatively intensity noise, crosstalk reduction, side-mode-suppressing ratio and power penalty of BER effect of the WRC-FPLD transmitted data are compared. The 200-GHz AWG filtered ASE injection minimizes the noises of WRC-FPLD based ONU transmitter, improving the power penalty of upstream data by -1.6 dB at BER of 10(-12). In contrast, the 50-GHz AWG channelized ASE injection fails to promote better BER but increases the power penalty by + 1.5 dB under back-to-back transmission. A theoretical modeling elucidates that the BER degradation up to 4 orders of magnitude between two injection cases is mainly attributed to the reduction on ASE injection linewidth, since which concurrently degrades the signal-to-noise and extinction ratios of the transmitted data stream.

A Weak-Resonant-Cavity Fabry–Perot Laser Diode With Injection-Locking Mode Number-Dependent Transmission and Noise Performances

Quasi-color-free weak Fabry-Perot cavity laser diode with long cavity length is one alternative solution of the wavelength-division-multiplexed passive optical network (WDM-PON) transmitter with comparable broadband gain spectrum and greatly reduced noise figure as compared to typical reflective semiconductor optical amplifiers. In this paper, the amplified spontaneous emission injection-locked weak-resonant-cavity Fabry-Perot laser diode (WRC-FPLD) with 1% front-facet reflectivity directly modulated at 1.25 Gbit/s with detuning injection-locked mode for quasi-color-free transmission in WDM-PON system with channel spacing of 200 GHz is demonstrated. With bias current changing from 0.9 Ith to 1.4 Ith, the improvement on receiving power sensitivity for the WRC-FPLD-based WDM-PON transmitter is up to 9 dB at bit error rate (BER) of 10-9. Increasing the injection-locked mode number from 2 to 3 within temperature variation of 6°C effectively promotes the BER from 10-8 to 10-10 at receiving power of -27 dBm associated with a decreasing power penalty of -3.2 dB. The WRC-FPLD with more injection-locked modes within one channel exhibits higher extinction ratio at higher operating temperature within one injection-locked-mode-number changing period. This elucidates well the cycling evolution on the BER performance of the WRC-FPLD as a function of operating temperature.

Reusing a Data-Erased ASE Carrier in a Weak-Resonant-Cavity Laser Diode for Noise-Suppressed Error-Free Transmission

Under injection-locking with downstream amplified spontaneous emission (ASE) carrier spectrally sliced by a 200-GHz arrayed waveguide grating and amplitude-squeezed by a gain-saturated semiconductor optical amplifier (SOA), the injection-level-dependent extinction ratio (ER) and bit-error-rate (BER) penalty of a weak-resonant-cavity Fabry-Perot laser diode (WRC-FPLD) upstream transmitter are investigated. By fixing the downstream power at -13 dBm, the downstream ASE data is amplitude-squeezed by the gain-saturated SOA to greatly suppress the ER from 12.6 to 2.2 dB, which improves the BER of upstream data carried by the reused ASE in the WRC-FPLD. By reusing the amplitude-squeezed downstream ASE carrier in the upstream WRC-FPLD, such a single ASE-based bidirectional channelized transmission network provides downstream and upstream receiving sensitivities of <;-27.5 and 21.8 dBm, respectively, at a BER of 10-9 after 25 km transmission.

10-Gbit/s direct modulation of a TO-56-can packed 600-μm long laser diode with 2% front-facet reflectance

A 600-μm long-cavity laser diode with a front-facet reflectance of 2% is demonstrated as a colorless OC-192 transmitter for the future DWDM-PON, which is packed in a TO-56-can package of only 4-GHz frequency bandwidth but can be over-bandwidth modulated with 10-Gbit/s non-return-to-zero data-stream. The coherent injection-locking successfully suppresses its side-mode intensity and noise floor level, which further improves its modulation throughput at higher frequencies. With increasing the coherent injection-locking power from -12 to -3 dBm, the side-mode suppression ratio significantly increases from 39 to 50 dB, which also suppresses the frequency chirp from -12 to -4 GHz within a temporal range of 150 ps. The dense but weak longitudinal modes (with 0.6-nm spacing) in the long-cavity laser diode suppresses to one single-mode in a 100-GHz wide DWDM channel for carrying the OC-192 data at 9.953 Gbit/s. Such an over-bandwidth modulated laser diode still exhibits an on/off extinction ratio of 6.68 dB and a signal-to-noise ratio of 4.96 dB, which can provide a back-to-back receiving power sensitivity of -12.2 dBm at BER of 10⁻⁹. After 25-km DSF transmission of the OOK data-stream at a bit rate up to 10 Gbit/s, the receiving power sensitivity is -10.1 dBm at a requested BER of 10⁻⁹.

Saturated signal-to-noise ratio of up-stream WRC-FPLD transmitter injection-locked by down-stream data-erased ASE carrier.

By controlling the extinction ratio (ER) and overshooting level of the down-stream amplified spontaneous emission (ASE) with a gain-saturation semiconductor optical amplifier (SOA), the down-stream data-erased ASE carrier is re-encoded in an injection-locked weak-resonant-cavity Fabry-Perot laser diode (WRC-FPLD) up-stream transmitter to implement all-ASE based bi-directional WDM-PON system. The effect of ER on the up-stream transmission performance of the down-stream data-erased ASE injection-locked WRC-FPLD is elucidated via the gain-saturation model. It is observed that the communication criterion with a bit-error-rate of <10⁻⁹ at 2.488 Gbit/s can be met only when ER is reduced to <3 dB and overshooting level <-5 dB. The up-stream WRC-FPLD re-encoded ASE data-stream could improve its signal-to-noise ratio (SNR) to 6.4 dB by minimizing the ER and overshooting level of the down-stream data-erased ASE to 2.4 dB and -7.8 dB, respectively, with the gain-saturated SOA. The SNR can also be improved with higher power injecting into the up-stream transmitter until saturation occurs and the optimal window of the ASE injection power is between -7 and -3 dBm.

Suppressing Chirp and Power Penalty of Channelized ASE Injection-Locked Mode-Number Tunable Weak-Resonant-Cavity FPLD Transmitter

The BER and noise characteristics of 1.25Gbit/s directly modulated ASE injection-locked mode-number tunable weak-resonant-cavity laser diode transmitter for WDM-PON system with channel spacing of 200GHz are characterized.

Compromised extinction and signal-to-noise ratios of weak-resonant-cavity laser diode transmitter injected by channelized and amplitude squeezed spontaneous-emission.

By using a 200GHz AWG channelized ASE source in connection with a saturable semiconductor optical amplifier (SOA) based noise blocker as the injecting source at the remote node in front of the local optical network units (ONUs), we demonstrate the spectrum-sliced ASE transmitter with greatly suppressed intensity noise performance in WDM-PON network. Such channelized SOA filtering technique effectively reduces the relative intensity noise of the ASE source by at least 4.5 dB. The low-noise WRC-FPLD transmitter improves its extinction-ratio (ER) from 8.9 to 9.6 dB and signal-to-noise ratio (SNR) from 5.9 to 6.3 dB. In comparison with broad-band ASE injection-locked WRC-FPLD transmitter at same power, there is an improvement on receiving power penalty (DeltaP(Receiver)) by 2 dB at BER 10(-9) in back-to-back case, and the receiving power of BER 10(-9) can achieve -24 dBm even after 25km fiber transmission. With additional AWG filtering, the intraband crosstalk effect between the upstream transmitted data and the reflected ASE signal is significantly reduced by 6.3dB. The compromised effects of ER and SNR on BER performance are also elucidated via the modified SNR model for the WRC-FPLD under ASE injection induced gain-saturation condition. The DeltaP(Receiver)/DeltaSNR of 8.89 at same ER condition is more pronounced than the DeltaP(Receiver)/DeltaER of 3.17 obtained under same SNR condition, indicating that the SNR plays a more important role than the ER on enhancing the BER performance.

Coherent Injection-Locking of Long-Cavity Colorless Laser Diodes With Low Front-Facet Reflectance for DWDM-PON Transmission

Long-cavity colorless laser diodes with different front-facet antireflection (AR) coatings are employed to perform the wavelength injection-locked ON-OFF-keying (OOK) data transmission. By changing front-facet reflectance of laser diode from 0.2% to 1.2%, the received OOK data enhance its Q factor by 6.3% and reduces its bit error rate (BER) by more than two orders of magnitude, which benefits from the improved signal-to-noise ratio and extinction ratio by up to 8.0%. Enlarging the injection-locking power from -6 to -3 dBm essentially helps the long-cavity colorless laser diode to promote its receiving power sensitivity from -27.9 to -29.2 dBm at BER of 10-9. However, the similar device with lower AR reflectance shows an opposite trend. The injection-locking-induced enhancement is limited within a frequency region controlled by the injection power, which results from a large disparity between continuous-wave injection and stimulated emission inside the long-cavity colorless laser diode. At same biased current and front-facet reflectance, a higher injection level provides a larger modulation throughput at a cost of decreasing bandwidth. The overinjection causes a limitation on frequency bandwidth of the long-cavity colorless laser diodes with lower front-facet reflectance. The numerical simulations with modified rate equations for the injection-locked long-cavity colorless laser diode with lower front-facet reflectance also elucidate that the transmission degrades distinctly at larger injection powers.