M.J. Guy

Efficient cascaded Raman generation and signal amplification at 1.3 μm in GeO2-doped single-mode fibre

We demonstrate a high-gain, cascaded fibre Raman amplifier, operating at 1.3 pm. Raman generation and amplification are achieved in a ring resonator constructed solely from fused fibre WDM couplers with low-loss GeOz-doped single mode fibre used as the active medium. The amplifier is pumped by a Nd:YAG laser at 1.064 p.m. In our resonant cascaded geometry, this generates the third Stokes line at 1.24 pm, which acts as a pump for Raman amplification of signals around 1.3 km. A gain of 28 dB is demonstrated with output signal powers of up to 20 dBm for 3.4 W of pump power. Our experiments also indicate the important role of filters to suppress feedback in the resonator, permitting high Raman gain and good signal quality. 0 1997 Elsevier Science B.V.

A duration-tunable, multiwavelength pulse source for OTDM and WDM communications systems

We describe a highly flexible ultrashort optical pulse source capable of generating duration-tunable pulses at single or multiple wavelengths. The technique we report is based on the filtering of the broad spectrum of femtosecond solitons which are generated using an electroabsorption modulator combined with nonlinear compression. The simplicity and robust nature of this source make it highly stable and we demonstrate the generation of pulses at a repetition rate of 10 GHz with durations in the femtosecond and picosecond regimes and the simultaneous generation of eight 10-GHz channels of picosecond pulses with a channel spacing of 3.5 nm.

Demonstration of the possibility of > 100 Gbit/s transmission over 77 km of standard fibre using a super-step-chirped fibre grating dispersion compensator

3.8 ps pulses at 1556 nm are reconstructed after transmission over 77 km of standard fibre using a 20 cm long super-step-chirped fibre Bragg grating. We show that good results can be obtained despite the fact that the grating was untrimmed and unapodised, even when the full 1.5 nm reflection bandwidth of the grating is used.

Fibre mopfa source of femtosecond pulses with wavelength tunability from 790 to 830 nm

A fibre-optic of sub-150 fs pulse with wavelength tunability from 790 to 830 nm is demonstrated. The output from a gain-switched DFB laser diode at 1552 nm is amplified and compressed in an EDFA generating a soliton-Raman continuum which was then frequency doubled. The output wavelength was tuned over a 40 nm range with very little variation in the pulse duration and output power.

A 10-GHz 1.9-ps actively mode-locked fiber-integrated ring laser at 1.3 /spl mu/m

We have reported a novel 10-GHz actively mode-locked laser operating at 1.3 /spl mu/m. The cavity design utilized a discrete semiconductor laser amplifier as the gain medium and an electroabsorption amplitude modulator. The laser was found to be tunable over a range of 10 nm and generated near transform-limited pulses as short as 1.9 ps.

A 1O-GHZ 2-ps actively modelocked fiber-integrated semiconductor laser employing an electroabsorption modulator

Recent efforts on semiconductor laser-based high-speed WDM-TDM systems have focused on the use of semiconductor laser array devices. Single-stripe semiconductor lasers, on the other hand, have been thought as unfeasible for simultaneous multiwavelength oscillations owing to the strong gain competition between the oscillating modes. In this paper, we demonstrate a WDM semiconductor laser source based on a singlestripe semiconductor traveling wave optical amplifier that generates four WDM channels simultaneously. Specifically, by active harmonic modelocking a grating-loaded external cavity laser system at 2.5 GHz, stable pulses have been generated at four wavelengths simultaneously. Pulsewidths of -18 ps have been demonstrated for the composite fourwavelength output, and for each individual wavelength output. We observed that active modelocking-induced transient unsaturated gain is the key mechanism underlying the stable multiwavelength picosecond pulse generation in a single-stripe semiconductor laser device. Figure 1 schematically shows the setup of the four wavelength laser. Actively modelocked optical pulses are generated from the laser diode by incorporating an intracavity spectral filter to define the individual spectral components. Wavelength tuning can be realized by translating the spectral filter vertically DIAGNOSTICS

A novel optical pulse compressor with use of a comb-like dispersion profiled fiber

Electroabsorption modulators (EAM) are proving to be very attractive pulse sources for high bit-rate communications systems.

Ultrahigh Bit Rate Generation and Applications

Various techniques are described for the generation of high repetition rate, high quality soliton pulse trains in the range 10 GHz to 1 THz. Emphasis is placed on the technique of nonlinear conversion of an optical beat signal in dispersion modified fibre. In addition, self-Raman scattering has been demonstrated as a powerful technique for ultrashort pulse generation and excellent mark space ratio operation. Techniques based on phase modulated sideband extraction and direct modulation using electro-absorption modulators operating in the 10 GHz – 60 GHz regime are also described.