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The authors report a method for measuring WDM components that uses a lightwave synthesised frequency sweeper. A measurement time of 2s per channel, a frequency accuracy of /spl plusmn/20 MHz, a resolution of 1 GHz and a dynamic range of 50 dB were simultaneously achieved.

A stable lightwave frequency synthesiser has been realised by combining discrete-time negative frequency feedback with a polarisation diversity technique. It is confirmed that this synthesiser operated stably for 24 h by using an optical frequency counter with 100 MHz accuracy.

A broadband lightwave synthesised frequency sweeper has been realised. An acousto-optic frequency shifter with a large frequency shift (1 GHz) and a synchronously tuned bandpass filter in an amplified fibre optic ring were employed, and a frequency sweep span of 1.1 THz was acheived.

The authors have demonstrated 15 dBm output Pr/sup 3+/ doped fluoride fibre amplifiers (PDFAs) pumped by two high-power, and wavelength stabilised, InGaAs semiconductor lasers and also the low noise characteristics of AM-VSB video signal transmission using a PDFA. The wavelength of the InGaAs pumping semiconductor lasers was locked through fibre Bragg gratings, resulting in a reduction of the white-line noise in a CATV experiment, which is caused by the mode-hopping of the pumping sources.

Singlemode polymer optical waveguides are fabricated using fluorinated polyimides. The optical waveguides exhibit a low loss of less than 0.3dB/cm parallel to the waveguide plane (TE polarisation) at 1.3μm, and have thermal and moisture stability.

Two types of polymer ridge optical waveguide are prepared using new fluorinated polyimides with excellent transparency and refractive index controllability. One has a polyimide core with a refractive index n of 1.573 and an SiO2 undercladding layer. The other has a polyimid e core (n = 1.521) and a polyimide undercladding layer (n = 1.520). These waveguides exhibit a low loss of 0.3dB/cm at 1.3μm. In addition, they have high thermal stability because of high temperature curing (above 350°C).

The influence of impurities on hydrogen-induced OH loss increase and radiation-induced loss increase is examined in GeO2-doped SiO2 fibres with a synthetic SiO2 clad. Fibres contaminated by both aluminium and sodium ions show loss increases as great as fibres with a natural SiO2 clad.

The radiation-induced loss in optical fibres drawn at speeds of 120 to 860 m/min and at furnace temperatures of 2000 to 2255°C is examined. It is found that the loss decreases with increasing drawing speed and with decreasing furnace temperature, and is caused by drawing-induced defects.

Hydrogen-induced loss in the hydroxyl absorption band is found to be reduced by accelerating the drawing speed and by depressing the furnace temperature. By analysing the thermodynamic behaviour of defects during the drawing process, sites reactive with hydrogen causing this loss are shown to be drawing-induced defects.

A high Young's modulus, low-linear-expansion-coefficient-polymer loose-jacket optical fibre has been developed using orientated polyoxymethylene (POM), which exhibits Young's moduli 20 to 40 GPa and linear expansion coefficients ? 10?6°C?1. The highly orientated POM loose-jacket fibre has no microbending losses in a temperature range ?60 to 80°C.

Drawing-induced defect centres are investigated in pure silica optical fibres drawn from the preforms consolidated in O2-including atmospheres. The drawing-induced E? centres decrease while the peroxy radicals increase with increasing flow rate of O2 into the consolidation furnance. The ?-ray-induced loss of these fibres is also examined.

The transmission loss at low temperature of an optical fibre tightly jacketed with a new low-linear-expansion-coefficient plastic, thermotropic liquid-crystal polymer, is reported. The new type of tight-jacket fibre is free from microbending losses due to jacket contraction when exposed to heat cycles from ?70 to 80°C.

The fibre strain change for an oriented liquid-crystal polyester-jacket optical fibre has been examined over the temperature range 20 to 120°C. Because of the low linear expansion coefficient and the absence of orientation release, the fibre strain change during the heat cycle is very slight, and accordingly no microbending loss is induced.