Low-noise single-photon detection at wavelength 1.55 μm

The photon-counting performance of commercially available InGaAs/InP avalanche photodiodes operated in Geiger mode was investigated at temperatures between 77 and 260 K. In particular, their noise equivalent power was measured to be 4×10^-17 WHz ^-1/2 at 77 K. The implications of these results in the context of a quantum cryptography application are discussed     

A carrier injection type optical switch in GaAs using free carrierplasma dispersion with wavelength range from 1.06 to 1.55 μm

The switching current for the device is about 90 mA at all in-range wavelengths. Its broad wavelength range is suitable for optical signal-processing applications in wavelength-division multiplexing transmission systems. High coupling efficiency to a single-mode fiber is achieved by using a small-Δ waveguide structure with carrier blocking layers. The effective refractive index change in the waveguide per unit of the injected current density is doubled by the carrier blocking layers without reducing coupling efficiency     

Polarization independent narrow channel wavelength divisionmultiplexing fiber couplers for 1.55 μm

A polarization-independent narrow-channel (PINC) wavelength division multiplexing (WDM) coupler for operation at 1.55 μm has been designed based on the birefringent properties of fused single-mode couplers. These couplers are made from both conventional single-mode fiber (SMF) and dispersion shifted fiber (DSF). The couplers are designed so that the coupling-coefficient-length products for the two orthogonal polarizations are π out of phase. As a result of the long coupling lengths required, these couplers have very small cross-sectional dimensions, typically on the order of 10 μm     

1.55 μm wavelength region high-stability optical fibre lossvariation measurement using fibre coupler

A 1.55 μm-wavelength high-stability optical fibre loss variation measurement system, using a comparison method with an optical fibre coupler, was developed. Long-term stability within ±0.001 dB over a 120 hour period at a room temperature variation of ±2.2°C has been achieved     

1.55 μm polarisation independent semiconductor optical amplifierwith 25 dB fiber to fiber gain

Using a tapered in width square active waveguide and bulk InGaAsP/InP material we demonstrate a polarisation independent amplifier structure operating at 1550 nm with a reduced far-field divergence. Improvement of coupling efficiency enables us to achieve a 25 dB fiber to fiber gain together with 9 dBm fiber saturation output power for 150 mA bias current. A 200 ps gain recovery time allows fast gating or wavelength conversion     

An optical fiber amplifier for wide-band wavelength range around1.65 μm

The optical amplification characteristics of a 0.781-μm pumped thulium-doped fiber in the wavelength range of 1.6-1.7 μm are discussed. A maximum net gain of 2.0 dB was obtained for 1.69-μm operation. This optical fiber amplifier is suitable for in-service monitoring and identifying fibers operating at 1.2-1.6 μm     

Guided-wave 1.3/1.55 μm wavelength division multiplexer based onmultimode interference

To improve the wavelength sensitivity of the multimode interference phenomenon and thus reduce the device length, a restricted-resonance multimode interference scheme and a lower beat length ratio were adopted to design a novel 1.3/1.55 μm wavelength division multiplexer. Using the modal propagation analysis, transmission characteristics of the device were investigated     

10-Gbt/s soliton communication systems over standard fiber at 1.55μm and the use of dispersion compensation

The limits to soliton propagation at 10 Gbt/s in standard fiber systems at 1.55 μm are assessed. We show that propagation for up to 200 km is possible using 36-km amplifier spacings and 30-ps solitons. In order to extend this distance and increase the range of usable pulse widths, the use of dispersion compensating fiber, as part of each amplifier, is evaluated. In addition this scheme significantly reduces the average power requirements     

1-mW CW-RT monolithic VCSEL at 1.55 μm

In this letter, we demonstrate the first result of a high-power (1 mW) continuous-wave room-temperature vertical-cavity surface-emitting laser emitting at 1.55 μm using a single InP substrate. The whole structure was grown monolithically using gas source molecular beam epitaxy and incorporates two original approaches. The first originality consists in the growth of a metamorphic GaAs-AlAs Bragg mirror directly on an InP-based cavity. The second novel idea is to use a tunnel junction for current injection. Moreover by using these two approaches the processing is very simple and, therefore, fulfills the goal for low-cost laser production in access and interconnections applications     

1.5 μm two-section Fabry-Perot wavelength tunable optical filter

A 1.5 μm two-section Fabry-Perot wavelength tunable optical filter is studied. As opposed to DFB filters, this wavelength tunable optical filter has the advantage that the wavelength tuning range and the transmission bandwidth can be designed independently. This two-section Fabry-Perot filter also controls the transmissivity (gain) and the transmission wavelength independently by current injection and the constant-gain and constant-bandwidth wavelength tuning is achieved. The wavelength tuning range is as wide as 188 GHz (15 Å), the constant-gain is as high as 23 dB and the constant-bandwidth is as narrow as 5 GHz during wavelength tuning. A 25-channel wavelength selection with less than -10 dB crosstalk is expected with this filter     

A new single-polarization optical fiber

In the single-polarization optical fiber, two isolated stress-applying parts contribute to radiate one of the two orthogonal polarization modes due to the asymmetrical geometric-index effect in addition to a stress-induced birefringence effect without bending the fiber. The loss spectra for x- and y-polarizations and the length dependence of the crosstalk show that the present fiber exhibits single-polarization characteristics     

Generation of millimetre and sub-millimetre waves by photomixing in1.55 μm wavelength photodiode

A 70 GHz bandwidth commercial photodiode has been used to create a photomixer source of radiation at frequencies from 70 GHz to above 600 GHz. The waveguide source is driven by two 1.55 μm lasers and delivers a peak, nonsaturated, power of -7.5 dBm at 110 GHz with a power conversion efficiency above 1%. Detected power decreases approximately as 1/(frequency)⁴ above 150 GHz     

Chromatic dispersion measurement in 1.55 μm narrow-band regionusing a tunable external-cavity laser

Measurement of the chromatic dispersion of an 80.6-km-long, concatenated, dispersion-shifted, single-mode fiber (DSF) with a tunable 1.55-μm external-cavity laser diode, using the phase-shift technique at 1.55 μm over 80-nm bandwidth, is discussed. It is shown that the technique does not need intricate curve-fitting equations or a large number of laser sources with specified wavelengths. As a result, the measurement configuration and procedure are relatively simple. The technique is useful for measuring the chromatic dispersion of future advanced fibers such as dispersion flattened fibers with various refractive index profiles     

Deep sea trial of 1.55 μm optical fibre submarine cable system

The first 6000 m deep sea trial of a 1.55 μm optical fibre submarine cable system was successfully conducted in the Pacific Ocean, near Torishima Island, in January 1988. By using 1.55 μm loss-minimised single-mode fibre cables and submerged fully monolithic Si-IC regenerators with DFB lasers, excellent transmission performances at 140, 280 and 565 Mbit/s were obtained through 150 km repeater spacings, respectively     

Injection-locked 1.55 μm VCSELs with enhanced spur-free dynamicrange

Injection locking is demonstrated to improve the analogue performance of long wavelength VCSELs. The third-harmonic spur-free dynamic range was improved by 9 dB/Hz^2/3 to be 93 dB/Hz^2/3, and the modulation bandwidth was increased twofold     

Design of single-polarization single-mode photonic crystal fiber at 1.30 and 1.55 /spl mu/m

Single-polarization single-mode (SPSM) operation of a highly birefringent (HB) photonic crystal fiber (PCF) is investigated in detail by using a full-vector finite-element method (FEM) with anisotropic perfectly matched layers (PMLs). The cutoff wavelengths of the two linearly polarized principal states can be designed by varying the structure parameters of the PCF. The confinement loss and splice loss to standard single-mode fiber for particular SPSM PCFs are calculated and optimized at both 1.30 and 1.55 /spl mu/m.     

Analysis of the attenuation ratio of MQW optical intensitymodulator for 1.55 μm wavelength taking account of electron wavefunction leakage

A theoretical analysis of an attenuation ratio for MQW optical intensity modulator was carried out taking account of the leakage of electron envelope function from the well layer. In the MQW modulator using InGaAsP material, the leakage of electron envelope function is large even for a low applied field because of the comparatively low potential barrier for electron. A normalization scheme in energy space was introduced for such leaky envelope function and field dependence of the Stark shift and oscillator strength have been analyzed by solving exciton effective mass equation. This approach was applied to MQW modulator for the wavelength of 1.55 μm for optical communication system. The well width and well number for large attenuation ratio with small residual absorption have been obtained. The calculation was compared with the experimental result and the difference was discussed     

Predistortion of electroabsorption modulators for analog CATVsystems at 1.55 μm

A predistortion circuit with adjustable amounts of third- and fifth-order predistortion is studied both theoretically and experimentally. The circuit is used to cancel the third- and fifth-order intermodulation distortion of a 1.55-μm integrated electroabsorption modulator/DFB laser. The CSO obtained is -61 dBc and the CTB is reduced 22.6 dB to -65 dBc. This performance is maintained after fiber amplification and propagation through 13 km of nondispersion shifted fiber due to the modulator's low chirp. Dithering of the DFB laser's injection current is employed to increase the stimulated Brillouin scattering (SBS) threshold to +13.4 dBm     

All-optical 1.5 μm to 1.3 μm wavelength conversion in awalk-off compensating nonlinear optical loop mirror

We demonstrate highly efficient all-optical conversion from 1.5 μm to 1.3 μm using a novel nonlinear optical loop mirror that compensates for walk-off. We make the fiber loop by splicing alternating segments of standard single-mode and dispersion-shifted fibers and choose their lengths such that the walk-off of the 1.3 μm and 1.5 μm pulses in one segment is completely reversed in the adjacent segment. We also show that the width of the converted pulses can be tailored by this scheme     

Tensile-strained InGaAs/InGaAsP quantum-well optical amplifierswith a wide spectral gain region at 1.55 μm

A tensile-strained InGaAsP/InP multi-quantum-well optical amplifier is constructed which has ⩾92 nm bandwidth at 16-dB gain for 50-mA drive current. The wide gain bandwidth is a result of both n=1 and n=2 contributions from the e→1 h transition. These results suggest wide tunability for lasers made from this material