A linearized optical directional-coupler modulator at 1.3 μm

We investigate electrooptic directional-coupler modulators operating at the wavelength of 1.3 μm, to have high linearity in their response function. The inverse Fourier transform technique was used to synthesize the spatially varying coupling function from a specified response function. The resulting coupling function was then used to determine the shape of the modulator structure. Modulators to have the response function of the form of a triangular (“linear”) function have been designed, fabricated, and tested. The third-order intermodulation-limited spurious-free dynamic range, at -130-dBm normalized noise floor, of 96.2 dB/Hz^2/3 was obtained     

Lossless InAsP-InGaP modulator at 1.3 /spl mu/m for optical conversion of radio signals up to 40 GHz

We report on an InAsP-InGaP electroabsorption modulator at 1.3 /spl mu/m integrated with a semiconductor amplifier. The fiber-to-fiber insertion gain reaches +10 dB. The 50-/spl mu/m-long modulator section exhibits a bandwidth of 36 GHz and a -17-dB extinction ratio with 3-V drive voltage. The integrated amplifier produced an RF-link efficiency of -26 dB at 20 GHz without any external amplification.     

15 GHz bandwidth quantum well electron transfer intensity modulator at 1.55 mu m

A barrier reservoir and quantum well electron transfer intensity modulator is reported, which operates at 1.55 mu m with the largest electrical bandwidth reported to date, 15 GHz. More than 20 dB extinction is obtained at 1.55 mu m for both TE and TM polarisations.<>     

Vertical-cavity amplifying modulator at 1.3 μm

The modulation/switching properties of a vertical-cavity semiconductor optical amplifier operating at 1.3 μm wavelength are investigated. The device was optically pumped and operated in reflection mode. A 150-mV (100 mA) modulation of the drive to the pump source produced a 7-dB modulation of the pump power, which produced a 35-dB modulation in the output signal. The maximum extinction ratio was 35 dB, and limited by device heating. Frequency response measurements revealed a modulation bandwidth of 1.8 GHz when the amplifier was saturated. This enabled 2.5-Gb/s modulation of a -10 dBm input signal with 5.5-dB fiber-to-fiber gain     

Bidirectional, subcarrier-multiplexed transmission using 1.3-/spl mu/m Fabry-Perot lasers

We demonstrate a full-duplex, subcarrier-multiplexed, transmission system which employs 1.3-/spl mu/m Fabry-Perot strained layer MQW laser diode transmitters in both directions. Coherent effects are reduced by using lasers with different mode spacing.     

Time-domain modeling of mode suppression in 1.3-/spl mu/m Fabry-Perot lasers

Fabry-Perot lasers still comprise the bulk of lasers used in optical fiber systems. The spectral envelope, of the Fabry-Perot modes, can be modulated either deliberately or as a consequence of processing stages. This can be beneficial, in the case of modal sculpturing where specific Fabry-Perot modes are suppressed, or a hindrance in the case of poor devices. A time-domain model is used to model 1.3-/spl mu/m Fabry-Perot lasers. Simulated power conserving reflective sites are introduced between sections in the model to simulate the effect of reflective sites from etch pits on the output characteristics of real lasers. Spectral modulation of the laser output is reported in agreement with previous experimental results and the strength of reflections required is investigated. We also report the use of the model to investigate the effect of fiber dispersion on the modulated laser output with different spectral mode modulation.     

Silicon Mach-Zehnder waveguide interferometers operating at 1.3 mu m

Mach-Zehnder waveguide interferometers have been fabricated in silicon and operation has been demonstrated at lambda =1.3 mu m. The switching mechanism is based on the thermally induced variation of the refractive index of crystalline silicon. Modulation depths of 40% were obtained for switching powers of 30 mW and switching times of 50 mu s.<>     

GaAs PIN electro-optic travelling-wave modulator at 1.3 ?m

A GaAs PIN travelling-wave modulator operated at 1.3 ?m has been fabricated from material grown by organometallic vapour phase epitaxy (OMVPE) on an n+ (100) GaAs substrate. The device has a constant V? of 8 V from DC to 10 GHz and an optical extinction ratio of 13 dB. The optical insertion loss of the device is 3.5 dB, and the 3 dB frequency bandwidth is measured to be 4.1 GHz, which is limited by the microwave slowing induced by the n+ substrate.     

Opening the 1.5 mu m window in 1.3 mu m regenerated systems

The authors introduce a novel upgrade technique for currently installed 1.3 mu m regenerated optical transmission systems that can be implemented with minimal disturbance to existing plant. The method uses erbium fibre amplifiers to bypass regenerators thus opening the 1.5 mu m window. The concept is discussed and an experiment reported to illustrate the scheme.<>     

Autocorrelation at 1.3-1.5 mu m using POM crystal

A nonlinear 3-methyl 4-nitropyridine 1-oxide (POM) crystal is used in a collinear type-I autocorrelator for the measurement of picosecond pulses generated by 1.3-1.55 mu m semi-conductor lasers. Experiments were performed at 1.3 mu m. Measurements of laser pulses with peak powers as low as 300 mu W are reported.<>     

Polymer channel waveguides with low loss at 1.3 mu m

Highly transparent polymers in the 0.6-1.3 mu m wavelength region have been synthesised from deuterated or halogenated methacrylate monomers. Low loss waveguides of less than 0.1 dB/cm at a wavelength of 1.3 mu m have been fabricated using the polymers.<>     

Amplification and lasing at 1.3 mu m in praseodymium-doped fluorozirconate fibres

Light emission from the /sup 1/G/sub 4/ to /sup 3/H/sub 5/ transition around 1.3 mu m of Pr/sup 3+/ has been studied in fluoride glass (ZBLAN) fibres. Pumping at 1064 nm yields extracted laser power of a few mW at 1.294 mu m. Gain curves centred at 1.295 mu m have been obtained, with gross gains of more than 15 dB at 1.319 mu m. Changes of the output ASE with pumping conditions are explained by excited state absorption or energy transfer from the /sup 1/G/sub 4/ upper level of the transition.<>     

Bulk Fabry-Perot intensity modulator for LIDAR systems

This letter reports on a built Fabry-Perot modulator operating at high optical intensities in the blue-green optical region. The design, fabrication, and characterization of a prototype modulator using LiNbO/sub 3/ as the host material with mirrors deposited directly on the end facets of the crystal are described. A measured modulation depth of 23.9% was achieved.     

Laser emission and amplification at 1.3 mu m in neodymium-doped fluorophosphate fibres

Laser emission and amplification have been studied in the 1.3 mu m spectral region on the /sup 4/F/sub 3/2/-/sup 4/I/sub 13/2/ transition in Nd/sup 3+/-doped fluorophosphate singlemode fibres. Pumping at 800 nm yields an extracted laser power of 10 mW at 1.323 mu m. A gain higher than 3 dB was obtained at the same wavelength in the amplifier experiment.<>     

1.3 mu m semiconductor laser power amplifier

The performance of a 3.4-Gb/s system using a low-power 1.318- mu m distributed-feedback (DFB) laser transmitter and a traveling-wave semiconductor laser power amplifier is studied. The -14.5-dBm, input from a directly modulated DFB laser is boosted to +10.3 dBm, of which +4.8 dBm is coupled into the transmission fiber. The penalty, caused by amplifier noise and pattern effects due to gain saturation, is less than 0.5 dB.<>     

High responsivity 1.3 mu m transceiver module for low cost optical half-duplex transmission

A pigtailed transceiver module which exhibits a record responsivity of 0.5 A/W is described. A single laser chip of Fabry-Perot type V-on-U-groove (VUG) laser is packed in a butterfly type package. By improving the fibre-chip coupling, a responsivity as high as 0.5 A/W is demonstrated together with a bandwidth of 1.5 GHz. The power penalty, compared with that of a p-i-n photodiode within the same experimental configuration, is only 1.2 dB at 800 Mbit/s.<>     

Wavelength conversion from 1.3 to 1.55 mu m using split contact optical amplifiers

Wavelength conversion of data from an optical carrier at a wavelength of 1.31 mu m to an optical carrier within the 1.5- mu m telecommunications window was demonstrated using a split-contact semiconductor nonlinear Fabry-Perot optical amplifier. Conversion was achieved by modulating the amplifier gain seen by a 1.55- mu m continuous-wave signal by saturating an absorber section using a modulated 1.31- mu m signal. Data transfer was possible from 1.31 mu m up to wavelengths between 1.53 and 1.585 mu m for bit-rates of up to 400 Mb/s. The maximum output contrast ratio was 3:1 and the minimum power at 1.31 mu m required for switching was approximately 60 mu W. By optically pumping the amplifier to above the lasing threshold using the 1.31- mu m signal, conversion was obtained to a fixed multiwavelength output with a 10-dB contrast ratio.<>     

35 dB optical gain at 2.716 mu m in erbium doped ZBLAN fibre pumped at 0.642 mu m

An optical gain of 35 dB at 2.716 mu m signal wavelength has been measured in an erbium doped ZBLAN fibre. A pump-wavelength scanning determined the pump wavelength for maximum gain. This pump wavelength was found to be 0.642 mu m. The maximum absorption wavelength for this Er/sup 3+/ doped fibre is 0.649 mu m. It was deduced that the excited state absorption process improves the gain performance of such fibres at the signal wavelength considered.<>     

A surface-normal coupled-quantum-well modulator at 1.55 /spl mu/m

We demonstrate a surface-normal coupled-quantum-well InGaAs-InAlAs electroabsorption modulator that provides optical modulation with a contrast ratio in excess of 1.5 at only 6 V. The device operates at 1.55 /spl mu/m and is based on a novel strain-balanced layer structure. The operating voltage is about two times lower than that of a conventional square quantum-well modulator that achieves a comparable contrast ratio.     

Quantum dot superluminescent diodes emitting at 1.3 /spl mu/m

We report ridge-waveguide superluminescent diodes based on five stacks of self-assembled InAs-GaAs quantum dots. Devices with output powers up to 10 mW emitting around 1.3 /spl mu/m are demonstrated. Spectral analysis shows a broad emission peak (26-nm full-width at half-maximum) from the dot ground state at low injection, and an additional peak from the excited state at higher bias. Temperature characteristics in the range 10/spl deg/C-80/spl deg/C are also reported. The experimental curves are in good agreement with simulations performed using a traveling-wave rate equation model.