Generation Of Transform-limited Optical Pulses Research Articles

Repetition-Frequency-Doubled Transform-Limited Optical Pulse Generation Based on Silicon Modulators

Compact and integrated optical pulse generation with a high repetition rate and a small duty cycle can benefit various applications such as integrated microwave photonics. In this work, a method to generate a repetition-frequency-doubled narrow optical pulse train based on two cascaded silicon Mach–Zehnder modulators is proposed and demonstrated. The generated frequency comb has even-order sidebands with linear phase and suppressed odd-order sidebands, which results in the transform-limited pulses in the time domain. The tunability of the repetition rate from 4.0 to 6.6 GHz and the duty cycle from 10.6% to 14.0% has been achieved. An analytic model that considers the non-ideal properties of the silicon modulators is also established and is able to reproduce the key features in the experiment. Our work shows the potential of an integrated silicon chip to generate high-speed optical pulse trains with tunable duty cycles demanded in integrated microwave photonics and integrated photonic signal processing.

1.2 ps pulses at low base repetition rates for 100Gbit/s per channel optical communications networks

The authors demonstrate the generation of transform-limited optical pulses with low background levels and durations tunable in the range 1 – 2 ps at readily selectable low base rates of 1 – 2.5 GHz. The system described is simple, compact and suitable for multiplexing up to 100 Gbit/s per channel.

Generation of transform-limited optical pulses using a combination of a gain-switched diode laser and a semiconductor optical amplifier

We introduce a novel method for generating nearly transform-limited picosecond optical pulses at multi-gigahertz repetition rates. Frequency-chirped optical pulses are first produced using a gain-switched semiconductor diode laser, and they are subsequently amplified by a semiconductor optical amplifier. The red frequency chirp in the gain-switched pulses is compensated for almost completely as a result of gain-saturation-induced self-phase modulation occurring in the amplification process. Experimentally, we have successfully generated nearly transform-limited 28-ps optical pulses at a 5-GHz repetition rate using a distributed feedback diode laser and a traveling wave semiconductor optical amplifier. >

Generation of transform-limited optical pulses up to 20 GHz from a monolithic electroabsorption modulator/DFB laser

Stable generation of transform-limited optical pulses using a monolithic electroabsorption (EA) modulator/DFB laser was demonstrated. The integrated device had a small α-parameter less than 0.3 and a wide electrical bandwidth over 20GHz. The time-bandwidth products of the generated optical pulses were less than 0.33 in the modulation frequency between 5 and 20GHz. Temporal forms of th e pulses were in good agreement with the sech2 pulse form. The over 4dBm output peak power was achieved from the EA modulator facet for 20GHz modulation frequency.

20 GHz transform-limited optical pulse generation and bit-error-free operation using a tunable, actively modelocked Er-doped fibre ring laser

The authors report the generation of 20 GHz, 3.0-3.5 ps transform-limited optical pulses across the wavelength tunable range 1550-1557 nm using a wavelength tunable, polarisation-maintaining actively modelocked Er/sup 3+/-doped fibre ring laser. Stable bit-error-free modelocking operation is confirmed throughout the wavelength tuning range.

Transform-limited optical pulse generation up to 20-GHz repetition rate by a sinusoidally driven InGaAsP electroabsorption modulator

The authors propose and demonstrate a simple technique for generating a transform-limited optical short pulse with variable repetition rates by using a sinusoidally driven InGaAsP electroabsorption modulator without any optical resonators. Using the pulse compression effect due to nonlinear attenuation characteristics of the modulator, a transform-limited optical pulse can be generated just with sinusoidal modulation. Theoretical calculations and experimental results show that the pulse shape is very close to the sech/sup 2/ shape, and the pulse width can be easily varied by varying the bias and modulation voltages. Transform-limited optical pulse generation with a minimum pulse width of 11 ps was achieved up to 20-GHz repetition rate. The time-bandwidth product was as small as 0.32. >

Invited paper Generation and control of transform-limited optical pulses in subpico- and picosecond regions from semiconductor diode lasers

In this paper we summarize and discuss a series of experimental investigations, performed systematically in recent years in our laboratory, for the generation of transform-limited optical pulses with excellent coherence in the picosecond and subpicosecond ranges from semiconductor diode lasers in the near-infrared wavelength region. The two basic methods, mode locking and direct modulation, were developed and fully studied for this first achievement employing AlGaAs and InGaAsP laser diodes. Active and passive mode locking incorporating external cavities with AlGaAs diode lasers were successful in realizing transform-limited optical pulses with durations of 30 ps and 0-58 ps respectively. Moreover, a strong RF modulation scheme superimposed on the forward and backward DC bias current was demonstrated to be the most practical and reliable for generating single-mode ultra short optical pulses with excellent coherence from a distributed feedback (DFB) InGaAsP diode laser. This transform-limited behaviour was...