Two-mode fibre spatial-mode converter using periodic coredeformation

Efficient conversion between the LP₀₁ and LP₁₁ modes in a two-mode fibre is achieved by periodically ablating the fibre surface with a CO₂ laser and then annealing the fibre with an electric arc. The resulting periodic core deformation produces 99% mode conversion over a 37 nm bandwidth around 1540 nm and 0.38 dB insertion loss     

Optical fiber up-tapers with index perturbations-performanceanalysis

The performance of step index up-tapers subjected to certain index perturbations in investigated by computer simulation. Concentric symmetric and asymmetric index profile perturbations as well as localized spherical, called regions bubbles, having a different index are studied. It is found that some low-valued perturbations of small scale size (less than a wavelength) do not alter the optical fiber performance. However, the amount of beam expansion in the up-taper may be ultimately limited by such perturbations. Excessive magnification in the presence of perturbations can cause a distortion of the quasi-Gaussian shape and symmetry of the pure step-index fundamental mode as well as increase the excess loss and degrade the lateral and axial displacement tolerance improvements of the up-tapers. For example, an index variation of Δn≈10^-5 in conjunction with a perturbation scale size of 40 μm can be detrimental. Bubble-type perturbations could also cause similar problems. A single 12.8-μm-diameter bubble with a relative index of -0.02, embedded in a 128-μm-diameter step index core with relative index of 0.5%, produced a 0.3-dB excess loss     

Elimination of signal distortion and crosstalk from carrier densitychanges in the shared semiconductor amplifier of multifrequency signalsources

The signals from multifrequency sources that utilize a shared semiconductor optical amplifier often exhibit distortion and crosstalk due to carrier density changes in the shared amplifier. We propose a technique that eliminates the signal distortion and crosstalk by keeping the carrier density in the shared amplifier constant via feedforward of the electrical drive signals. We demonstrate the technique using a waveguide grating router multifrequency laser     

Band-rejection fibre filter using periodic core deformation

Grating-based all-fibre bandstop filters were fabricated by introducing periodic deformations in the core of the fibre with a CO₂ laser by first ablating the surface of the fibre and then annealing it. These devices, which can be tailored to any wavelength, have a broad bandwidth (10 nm), high peak wavelength rejection (>20 dB), low insertion loss (<0.3 dB), a very flat response outside the rejection band, and a short physical length (6 mm)     

Packaged hybrid soliton pulse source results 70 terabit.km/secsoliton transmission

A packaged hybrid soliton pulse source is used in a soliton transmission experiment employing sliding-frequency guiding filters. The source shows excellent stability and very clean tuning characteristics. Control of the operating frequency and wavelength are described. Error free transmission at 10 GBit/s is achieved over a distance of 27000 km     

Quantum well electron transfer waveguide with high couplingefficiency to single-mode fiber

We demonstrate low fiber-waveguide coupling loss in a large optical mode barrier reservoir and quantum well electron transfer (BRAQWET) modulator. Electrooptic efficiency and propagation loss are comparable to those measured in a conventional waveguide structure with the same active material     

Simplified laser to fibre coupling via optical fibre up-tapers

A new method for coupling single-mode fibre to laser diodes employing a spherical ruby lens and a single-mode optical fibre up-taper is demonstrated. High coupling efficiency and greatly reduced alignment sensitivities are attained     

Semiconductor optical amplifier array coupled to uncoated flat-endfibers with integrated beam expanders and TiO2 antireflectioncoatings

We present a novel coupling scheme consisting of an integrated beam expander, a specifically tailored TiO₂ antireflection coating, optical index matching gel, and uncoated flat-end single-mode fiber (SMF). This scheme was used to package four-channel semiconductor optical amplifier arrays. Far-field profiles for each discrete amplifier in the array are typically 80 and 150 FWHM, perpendicular and parallel to the junction plane, respectively. The TiO₂ AR coating overcomes the indices mismatching of fiber glass and InP based device, and reduce optical reflection to 0.002% at 1.55 μm. Misalignment tolerance in the l-dB excess loss range, for a discrete channel, is typically 5 μm vertically and 8 μm laterally. The average coupling loss is 4.3 dB per facet for the devices measured. Fiber coupled small signal gain for the amplifiers is typically 11.6 dB and a saturation output power of 3.0 dBm. The method of characterization and optimization of the TiO₂ coating is discussed     

A 16×1 wavelength division multiplexer with integrateddistributed Bragg reflector lasers and electroabsorption modulators

The integrated operation of a 16×1 wavelength-division-multiplexed (WDM) source with distributed Bragg reflector (DBR) lasers and electroabsorption modulators has been demonstrated. By using repeated holographic exposures and wet chemical etching, 16 different wavelengths from 1.544 to 1.553 μm with an average channel spacing of 6 Å are obtained. A high-performance combiner is used to obtain a very uniform coupling into the single-output waveguide, and with the integration of an optical amplifier an average optical power of -8 dBm per channel is coupled into a single-mode fiber