Honglei Fan

Colliding pulse mode-locked laser

The fabrication and performance of a colliding pulse-mode locked laser with an intracavity saturable absorber is described. The laser has a threshold current of 65 mA and differential efficiency of 0.04 mW/mA when coupled into a single-mode fiber. Mode-locked pulses with /spl sim/1 ps pulse width at /spl sim/10 GHz has been obtained.

Small signal analysis of frequency response of four-wave mixing in semiconductor optical amplifiers

A theory of small signal frequency response of four-wave mixing (FWM) in a traveling wave semiconductor optical amplifier has been developed. The bandwidth of FWM is >300 GHz. For large wavelength separation between the input signals, where the nonlinear gain effects dominate the generation of FWM, the bandwidth of the FWM signal exceeds 1 THz.

Optical demultiplexing using semiconductor amplifiers

All optical demultiplexing of a 40 Gb/s signal into four channels at 10 Gb/s each and an 80 Gb/s signal into eight channels at 10 Gb/s each have been successfully demonstrated using four wave mixing and phase modulation in traveling wave semiconductor amplifiers. The latter is carried out with the amplifiers in a Mach-Zehnder configuration. Our calculations show that four wave mixing is expected to perform the demultiplexing function for signal speeds to 1 Tb/s.

Cross gain saturation in semiconductor optical amplifier

We have carried out gain saturation experiments using pulsed pump and probe beams derived from gain switched DFB semiconductor optical amplifier lasers. The widths of both pump and probe pulses were 35 ps. The gain saturation of the probe takes place only when there is temporal overlap of the pump and probe beams in the amplifier.

Digital and analog transmission through polymer optical fiber

For short distance communications, graded index polymer optical fiber has been proposed as the physical transport layer for high data rate networks. This paper reports the results of various transmission experiments through polymer optical fiber. Bit-error-rate of < 10-9 has been obtained after transmission through 200 m of polymer optical fiber at received optical powers of -22 dBm at 155 Mb/s and -19 dBm at 622 Mb/s respectively. The experiment utilized a 659 nm laser as the source and a Si photodiode as a detector. The measured power penalty due to modal noise of < 1 dB is in agreement with the calculated results. The performance of a hybrid AM/BPSK optical fiber transmission system has been investigated. A BPSK modulated 2 Mb/s pseudorandom digital channel is substituted for one of the AM channels in a 60-channel cable TV system. For the subcarrier modulated digital channel, a bit error rate < 10-9 is obtained after transmission through 200 m of fiber. The intermodulation distortion (IMD) effects using long and short fiber lengths have been studied. The results show that distortion caused by the laser non-linearity did not degrade the system at low modulation depth. However, as the modulation depth of the BPSK signal is increased, the distortion is more pronounced. The differences in the measured IMD between the long and the short fiber is negligible, suggesting the fiber-induced distortion in the transmission system is small.

Colliding pulse mode locked laser

The fabrication and performance of a colliding pulse mode locked laser is described. The laser has a threshold current of 5 mA and fiber coupled differential efficiency of 0.04 mW/mA. Mode locked pulses with /spl sim/1 ps width at /spl sim/10 GHz has been obtained.

Mode-locked InGaAsP laser

The fabrication and performance of a colliding pulse mode locked laser with an intracavity saturable absorber is described. The laser has a threshold current of 65 mA and differential efficiency of 0.04 mW/mA when coupled into a single mode fiber. Mode locked pulses with approximately 1 ps pulse width at approximately 10 GHz has been obtained.

Optical demultiplexing using semiconductor optical amplifiers

All-optical demultiplexing of a 40 Gb/s signal to four channels at 10 Gb/s each has been successfully demonstrated using optical four-wave mixing in a travelling wave semiconductor optical amplifier. It is also expected that any set of data bits up to 1 Tbit/s can be retrieved using the four-wave mixing process.

Four-wave mixing in a semiconductor optical amplifier

We have performed four wave mixing (FWM) measurements on a 2-section semiconductor optical amplifier (SOA) using CW and pulsed pump and probe beams. The FWM efficiency depends on the input pump power, the gain of the 2-section SOA and the wavelength separation between the pump and probe beams. A -19.1 dBm FWM signal power from the amplifier is achieved when the wavelength difference between the pump and probe beams is 2.5 nm. The pulse amplitude and pulse width of the FWM signal under the condition when the FWM signal is generated using pulsed pump and probe beams has been measured and analyzed. The results of the analysis are in agreement with the experimental data.

Cross Gain Modulation in Semiconductor Optical Amplifier

We have performed cross gain modulation measurements on a 2-section semiconductor optical amplifier (SOA) using pulsed pump and probe beams. The probe amplitude and pulse width under this condition has been measured and analyzed. The results of the analysis are in agreement with the experimental data. These results are important for all optical networks utilizing gain saturation in amplifiers for signal add/drop function.