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.

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.

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.

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.

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.