We have reported high power 40 Gbit/s electroabsorption modulators at 1550 nm and 1300 nm and their application to transmission over SMF-28. Time averaged output powers of up to 2.8 dBm were achieved with low dispersion penalty, allowing the generation of significant margin at 1550 nm, and 40-km loss limited transmission at 1310 nm. These results illustrate the huge potential for electroabsorption modulators in a wide variety of system applications including short reach, intermediate reach and dispersion managed systems.

A 40 Gbit/s electroabsorption modulator module with low drive voltage (2.1 Vpk-pk), low dynamic insertion loss (11 dB) and high optical output power (1 dBm) is described.

VCSELs are an important technology with many characteristics such as high modulation bandwidth, low-threshold currents and single-mode behaviour that make them suitable for telecommunications applications. InGaAsP/InP is one material system that has been used to manufacture devices that operate in the 1.55 μm region. However, the room temperature performance of VCSELs using this material system fall below those devices using AlGaAs/GaAs operating at shorter wavelengths. Therefore, it is of interest to investigate the temperature dependence of these long wavelength devices. In this paper we describe the experimental results on an array of 64 InGaAsP/InP VCSELs and ultra-bright LEDs designed to emit at 1.5 μm. We also take a simple theoretical model and compare the results with theory.

High performance operation is reported of fibre grating lasers which have a large spot, curved waveguide semiconductor reflective amplifier as the gain block. Devices incorporating both uncoated and antireflection coated chips show good linearity and temperature stability. Direct modulation at rates to 2.5Gbit/s is demonstrated.

The introduction of PCl3 into the MOVPE growth process dramatically alters the regrowth of InP around tall, narrow mesas. Planar regions 48 μm wide have been grown around vertical-walled mesas only 1 μm wide. Polycrystalline deposits are completely eliminated from the silica mask. Furthermore, this process has simultaneously produced planarised infilling growth of orthogonal channels. Electroabsorption modulators with low device capacitance and high modulation depth have been fabricated using this process, and have been used in systems operating at 100 Gbit/s

Long-wavelength vertical cavity surface emitting lasers (VCSELs) operating in the 1.3μm to 1.5μm wavelength range are ideal light sources for optical fibre communication applications. However, a number of problems have hindered progress in the development of cost-effective long wavelength VCSELs. These are (a) intrinsically high non-radiative losses, (b) difficulty in fabricating highly reflecting mirrors, lattice-matched to InP, and (c) the disparity between the predicted and observed temperature dependence of the operation of the devices. In this report we present the results of our studies concerning the pulsed operation of a bulk GaInAsP/InP VCSEL fabricated at BT laboratories. The device is tailored to emit at around 1.5 μm at room temperature. The structure has a 45 period n-doped GaInAsP/InP bottom Distributed Bragg Reflector (DBR), and a 4 period Si/Al 2 O 3 dielectric top reflector. Spectral electroluminescence (EL) from a 16 μm diameter window is measured in the pulsed injection mode. Device parameters are recorded in the temperature range between 90 K and 240K. Threshold current exhibits an approximate parabolic temperature dependence with a broad minimum of J th = 13.2 kA cm -2 , at temperatures between 170K and 195K. Temperature dependence of the threshold current is compared with the theoretical calculations which consider radiative transitions with and without k-selection. Best agreement with the experimental results is obtained when a partial k- selection model, with an energy broadening of about 4.4 meV, is used in the calculations.

A time-resolved photoluminescence study of strained and unstrained InGaAsP/InP double heterostructures has been performed at low photogenerated carrier densities (i.e. ≤1016 cm−3) using a novel high-efficiency germanium photon-counting detector. The photoluminescenee decay times are observed to decrease with increasing strain. Samples grown on substrates with lattice orientation (3 1 1)B are shown to have shorter excess carrier lifetimes than those grown on lattices orientated (0 0 1) or (3 1 1)A.

A curved waveguide, strained multiple quantum well reflective amplifier with an integrated front facet mode expander has been designed and fabricated. A device without facet coatings has been found to have a chip gain of 36dB with 6dB of gain ripple. This equates to an effective facet reflectivity of 8 x 10(-6).

An angled facet strained MQW semiconductor laser amplifier with integrated mode expanders has been designed and fabricated. A device with simple single layer antireflection coatings exhibited a maximum of 29dB fibre-to-fibre gain with a minimum noise figure of 7.2dB at 26dB gain and a saturation output power of 7.5dBm. This gain is equal to the highest reported for an SLA operating at 1.5 mu m while the noise performance is superior to that in any published work.

The authors report a wavelength tunable laser consisting of an in-line Fabry-Perot laser and lateral-grating assisted vertical codirectional coupled filter. The device can be tuned over 12 discrete 4 nm spaced longitudinal modes giving a total tuning range of 44 nm.

An angled facet strained MQW semiconductor laser amplifier with integrated mode expanders has been designed and fabricated. A device without antireflection coatings had <0.5 dB gain ripple and 0.5 dB polarisation sensitivity at 25 dB gain.

The authors report a grating assisted vertical coupler filter laser that uses a novel lateral grating to provide coupling vertically between the guides. This approach simplifies device fabrication. A wavelength tuning range of 58nm is reported.

The linearity of narrow-band RF and microwave analogue optical transmitters can be improved by re-modulating their output by using an intensity modulator with controllable nonlinearity. The authors demonstrate linearisation of a distributed feedback (DFB) laser using a monolithically-integrated electroabsorption (EA) modulator. The spurious-fret dynamic range of an un-optimised device is increased from 96 dBm/Hz(2/3) to 117 dBm/Hz(6/7).

In this paper, we present an investigation into factors that limited the median modulation depth of a batch of packaged discrete waveguide EA modulators to 23 dB at a wavelength of 1.55 /spl mu/m. Results from detailed measurements of the DC absorption and photocurrent spectra are used to show how stray parasitic light can perturb the absorption characteristic and reduce the modulation depth of these high-speed multiple-quantum-well modulators. A novel ridged deeply etched buried heterostructure EA modulator design is presented in which stray light is removed from the immediate vicinity of the guided mode. The key structural difference between these and the previous devices is that they employ a much thicker Fe-doped InP current blocking layer that was grown by atmospheric pressure MOVPE using PCl/sub 3/ for planarization. Detailed measurements of the DC absorption spectra of a packaged ridged deeply etched buried heterostructure device confirm that stray light causes only a minor perturbation on its absorption characteristics. Consequently the new batch of EA modulator modules have a higher median modulation depth of 40 dB, as well as lower fiber-to-fiber insertion losses and picosecond pulse generation capabilities that are very similar to the previous devices which were used in 40 Gb/s optically time division multiplexed experiments.

75% coupling to cleaved single mode fibre has been obtained for a 1.55 /spl mu/m tapered active strained MQW layer device. A fully packaged component using precision laser die cleaving and a silicon micro machined substrate has produced a record 55% passive coupling.

A fully packaged electroabsorption modulator is used to generate transform limited 4.1 ps pulses at a 20 GHz repetition rate. The feasibility of using this component for short pulse generation and demultiplexing in a four channel 80 Gbit/s OTDM system is discussed.<>