H. C. Bao

Impact of saturable absorption on performance of optical clock recovery using a mode-locked multisection semiconductor laser

This paper investigates the impact of saturable absorption (SA) on the performance of optical clock recovery using a mode-locked multisection laser diode. Optical clock at 40 GHz is recovered from the multisection laser with SA section operated under a range of bias conditions. The dependence of extinction ratio and timing jitter of the recovered clock on required optical injection power, data rate detuning, and mark ratio is also evaluated under these operation conditions. The experimental results show that strong SA effect in laser cavity improves extinction ratio and suppresses timing jitter of the recovered clock, while weak or no SA effect in laser cavity offers clock recovery with larger date rate detuning range defined by timing jitter and less dependence on the variation of data mark ratio for extremely low mark ratio.

Amplitude noise of subharmonically hybrid mode-locked pulses generated from a monolithic semiconductor laser

Broad-band amplitude noise (100 MHz to 20 GHz) of 40 GHz pulses generated by a subharmonically hybrid mode-locked (SHML) monolithic semiconductor laser is investigated. Experiments show that the amplitude noise can only be suppressed at some certain subharmonic numbers, while the phase noise can be suppressed by subharmonic hybrid mode-locking under many subharmonic numbers.

Transmission of Wavelength-Division-Multiplexed Channels With Coherent Optical OFDM

Transmission performance for wavelength-division-multiplexed (WDM) systems with coherent optical orthogonal frequency-division multiplexing is simulated including the fiber nonlinearity effect. The simulation shows that the system Q of the WDM channels at 10 Gb/s is over 13.0 dB for a transmission up to 4800 km of standard single-mode fiber without dispersion compensation

Multichannel dual-mode-based optical pulse source from a single laser diode

Generation of multichannel optical pulse trains by spectral slicing of two adjacent optical modes from a single subharmonically synchronous mode-locked laser diode is demonstrated in this letter. The obtained pulse source exhibits high extinction ratio (> 15 dB), low amplitude modulation (<-24.8 dB) and low timing jitter (< 0.5 ps) over all the channels from 1550 to 1564 nm. The resulting pulse trains can be used for the generation of carrier suppressed return-to-zero data in dense wavelength-division-multiplexed systems and optical generation of millimeter-wave signals required for future multiple channel fiber wireless systems.

Amplitude noise of 40-GHz pulses from a subharmonically synchronous mode-locked semiconductor laser

The broad-band amplitude noise of 40-GHz pulses from a subharmonically synchronous mode-locked (SSML) semiconductor laser is investigated. Experiments show that the amplitude noise of pulses generated from a SSML laser depends on the amplitude noise and pulsewidth of injected pulses, frequency detuning and subharmonic numbers.

Pulsed multichannel source generation for RZ based WDM application

This letter demonstrates a novel technique for the generation of a pulsed multichannel source from a multiple mode laser diode (LD). The pulsed multiple channel source with 6.5 GHz repetition rate was generated from a subharmonically hybrid mode-locked monolithic laser with 32.5 GHz mode spacing. The obtained pulse source exhibits high extinction ratio (>10 dB) and low level of root-mean-square (RMS) phase noise (<0.11 rad) over all channels from 1556 to 1565 nm. The proposed scheme is cost-effective and a promising candidate for 10-GHz pulse source generation in 10-Gb/s based wavelength-division-multiplexed (WDM) systems with 50-GHz channel spacing using return-to-zero (RZ) data format.

Suppression of amplitude modulation of pulses generated from a subharmonically mode-locked semiconductor laser

A feedforward modulation technique is used to suppress amplitude modulation associated with 40-GHz pulses generated from a subharmonically mode-locked semiconductor laser. It is shown that the amplitude modulation can be suppressed by as much as 20 dB. The improvement of amplitude modulation is shown for different subharmonic numbers.

Multichannel dual-mode pulse generation for DWDM and fiber-wireless system application

In this paper we propose a novel technique for the generation of wideband dual-mode pulses from a single subharmonically synchronous mode-locked laser diode (LD). The obtained pulse source exhibits high extinction ratio (>15 dB) and low timing jitter (<0.5 ps) over all the channels from 1550 to 1564 nm. The proposed scheme is cost-effective and a promising candidate as a pulse source for generation of carrier suppressed return-to-zero (CSRZ) modulation format in dense wavelength division multiplexed (DWDM) systems and optical generation of millimeter-wave frequency signals in multiple channel fiber wireless systems.

Effect of saturable absorption on the performance of a 40 GHz optical clock recovered from a monolithic semiconductor laser

The effect of a saturable absorber (SA) on the performance of 40 GHz optical clock signal recovered from a monolithic semiconductor laser is investigated, in terms of timing jitter, locking range, and extinction ratio. Experiments show that using a SA improves the extinction ratio but reduces the locking range and increases sensitivity to the data mark ratio.

Impact of monolithic saturable absorber on the performance of subharmonically mode-locked lasers at millimeter-wave frequencies

A detailed comparison of the characteristics of 40-GHz pulses from a subharmonic mode-locked monolithic laser diode with and without a saturable absorber (SA) is demonstrated in terms of timing jitter, frequency detuning, amplitude modulation, and extinction ratio. The experimental results show that saturable absorption in the laser cavity improves the extinction ratio and suppresses amplitude modulation and timing jitter, while no SA section in the laser cavity is cost-effective and offers subharmonically mode-locked pulses a larger frequency detuning range.