Single-mode, phosphorus-doped silica waveguides in siliconV-grooves

Single-mode, phosphorus-doped glass waveguides have been formed in silicon V-grooves by chemical vapor deposition. The fabrication process is reproducible, involves few steps, and produces waveguides with a loss on the order of 0.1 dB/cm at a wavelength of 0.633 μm. These waveguides are compatible with passive V-groove fiber alignment and out-of-plane coupling from integrated taps and end facets to surface-mounted optoelectronic devices     

Coloration and its reduction in phosphorus-doped low-loss optical fibres

Coloration and its reduction in phosphorus-doped low-loss optical fibres have been investigated. The absorption loss at 0.53?m is as high as 60 to 100 dB/km when measured immediately after the drawing process. The coloration, however, can be almost completely reduced by annealing at 100°C for 48 h.     

Pulse compression in optical fibres

A shift in the emission wavelength of s.h. GaAs lasers has been observed during individual pulses. In conjunction with material dispersion, this leads to pulse compression after transmission through an optical fibre. The use of this device as a source in bandwidth measurements readily leads to erroneous conclusions when results are analysed.     

Pulse delay measurements in single-mode fibers using sum-frequency mixing as a picosecond shutter

We describe a novel technique for measuring pulse delay in single-mode fibers. Relative time delay changes between different wavelengths are used to determine dispersion on both sides of the zero total dispersion wavelength. In this technique the sum-frequency mixing is used as a picosecond shutter. The measurement accuracy and the input power limitation to avoid the influence of stimulated Raman scattering for the measurement are described. Furthermore, dispersion characteristics on three single-mode fibers are measured, and it is pointed out from the experimental results that a larger refractive index difference and a shorter cutoff wavelength shift the zero total dispersion point toward the longer wavelength.     

Pulse broadening in near-square-law graded-index fibres

A closed-form expression for pulse broadening in graded-index fibres that have small and circularly symmetric, but otherwise arbitrary, deviations from a square-law, and arbitrary dn/d?, is applied to germania-doped fibres. The range of validity of the theoretical expression is defined by comparison with the results of numerical integration.     

Pulse broadening in multimode graded-index fibres

A closed-form expression is obtained for pulse broadening in graded-index fibres with k2(r)=1?r2+?2r4+?+?nr2n. Pulse broadening for k2(r)=1?r2+0.615r4+70r6 and r<0.1 is 12 times smaller than for square-law fibres if material dispersion is neglected.     

Pulse propagation in multimode optical fibres

Coupled mode theory is unnecessary for the analysis of pulse propagation in multimode optic waveguides. Instead, a very simple ray or continuum equation is derived from elementary plane-wave concepts to account for the effects of absorption loss and scattering. The formalism reduces to a diffusion equation for highly forward directed scatterers.     

Chlorine concentration profiles in silica fibres

Chlorine concentration profiles in silica fibres were studied by X-ray microanalysis and consideration of the chemical reactions concerned with chlorine in the fibre fabrication process. The chlorine content was proportional to the doped element contents. The Cl/Ge content ratio was larger than the Cl/Si or Cl/P content ratio.     

Pulse and time-domain measurements

A review of the state of the art and science of pulse parameter measurements is given including recent advances in the use of real-time oscilloscopes, waveform recorders, equivalent time sampling oscilloscopes, and counter timers in the measurement of repetitive and single transient signals. Recent advances in the use of artifact waveform standards and modern signal analysis techniques to compensate for measurement distortion are highlighted. The formation and progress of an IEEE committee which is developing a performance standard for waveform recorders is also described.     

Pulse distortion in single-mode fibres with microbending

The pulse distortion due to energy reconversion from higher-order modes into the fundamental mode in randomly bent single-mode fibres is calculated. Pulse distortion can be reduced by either introducing mode filters or by a sufficiently large attenuation of the higher-order modes. Simple design considerations are given.     

Temperature desensitisation of delay in optical fibres for sensor applications

We demonstrate a significant reduction in delay sensitivity against temperature in optical fibres, using a novel tight jacketed fibre structure. This technique has the cabability of producing fibre in which the optical delay is insensitive to temperature. This has potential in the field of sensors and fibre devices.     

Wavelength-dependent differential modal delay in graded-index fibres

We present a technique for measurement of wavelength-dependent differential modal delay in a graded-index fibre. The data are used to derive the excitation-dependent zero-dispersion wavelength. The method offers an accurate calibration procedure to determine the zero-material-dispersion wavelength for given dopant concentration.     

Optical processing technique for spot-size measurements in single-mode fibres

A new, simple and very promising technique for spot-size measurements in single-mode fibres is proposed, based on a spatial filter which modulates the optical beam at the output of the fibre. Its inherent simplicity, accuracy and high efficiency make it attractive for laboratory and factory measurements.     

Ultra-wide-band Raman amplifier using tellurite and silica fibres

An extremely large seamless gain-bandwidth of 135 nm (1497-1632 nm) with a minimum gain of 22.8 dB is achieved with a novel hybrid tellurite/silica fibre Raman amplifier. The amplifier is used successfully as a pre-amplifier in a WDM transmission experiment     

Pulse dispersion for single-mode operation of multimode cladded optical fibres

Pulse dispersions as low as 0.4 ns/km have been measured in multimode cladded fibres at a normalised frequency V=125 and for a constant bend radius of 5.5 cm. Particularly when the number of launched modes is small, the pulse dispersion, as well as the polarisation and angular width of the output beam, are strong functions of the degree of mode conversion.     

New absorption bands in pure and F-doped silica optical fibres

Two very narrow absorption bands positioned at 765 nm and at 1273 nm have been found in pure silica and fluorinedoped silica optical fibres. Their origin is probably connected with the preform production technique. Annealing of the preform and different fibre drawing conditions did not influence the absorption bands.     

Competition between second and third harmonic generation in silica fibres

Third harmonic generation could develop in silica fibres through a feedback process similar to that suggested for second harmonic generation. The initial susceptibility dictates the outcome of the competition between the two processes.<>     

Backscatter attenuation measurements in graded index fibres

A comparison is made of the attenuation values obtained by the backscattering technique and the more conventional cut-back method, and the backscattering technique is shown to provide highly accurate and reliable results.     

Pulse broadening in multimode fibres excited by GaAs lasers

Pulse dispersion in multimode fibres depends strongly on mode excitation at the input and mode coupling in the fibre. Measurements on fibres of up to 160 m in length are given: pulse dispersion seems to follow a square-root law with the lengths of the fibres.