Temperature dependence of the Kerr effect in a silica optical fibre

The temperature dependence of the electro-optic Kerr effect has been measured in a silica-cored monomode optical fibre. The Kerr constant was measured as 5.3×10?16 mV?2 at 23°C with a temperature coefficient of +0.56% per deg C over the range 23 to 88°C. This measurement has implications for optical-fibre temperature and electric field sensors.     

Fibre strain induced during heat cycle in liquid-crystal polyester-jacket optical fibre

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.     

Small-active-area germanium avalanche photodiode for single-mode fibre at 1.3 ?m wavelength

A germanium avalanche photodiode of 30 ?m active area diameter has been fabricated and tested. The multiplied dark current is as low as 5 nA at room temperature. A module using this diode and a spherical lens has been assembled and coupled with a single-mode fibre of core diameter 10 ?m. The quantum efficiency of the module is 90% at 1.3 ?m. The sensitivity is measured at 45 Mbit/s and at 1.3 ?m. Minimum detectable powers obtained for 10?11 error rate are ?51.9 dBm and ?50.7 dBm at 25°C and 50°C, respectively.     

Refractive index dispersion of lightguide glasses at high temperature

The refractive index of pure and GeO2-doped silica glasses was measured at wavelengths from 0.4 ?m to 2.1 ?m, over a temperature range from 20°C to 540°C. Values for the thermal coefficient of the refractive index (about 1.2×10?5/°C at 1.3 ?m) were almost identical for both glasses. The data showed that material dispersion for optical fibres increases with increasing temperature.     

Optical fibre jacketed with high-modulus low-linear-expansion-coefficient polymer

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.     

Transmission loss of thermotropic liquid-crystal polyester-jacketed optical fibre at low temperature

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.     

High-power single-mode optical-fibre coupling to InGaAsP 1.3 ?m mesa-structure surface-emitting LEDs

High-power single-mode optical-fibre coupling to LEDs has been achieved by novel mesa-structure InGaAsP 1.3 ?m surface-emitting LEDs. A ?26.7 dBm (2.1 ?W) fibre-coupled power has been obtained with 210 MHz optical ?3 dB modulation bandwidth at 23°C 50 mA current. The 140 Mbit/s transmission feasibility over a single-mode optical fibre has been studied.     

Chemical change from diffused hydrogen gas to hydroxyl ion in silica glass optical fibres

The chemical change from hydrogen gas that diffuses into silica glass for optical fibres to hydroxyl function has been investigated. Hydrogen molecules that diffuse into GeO2-doped silica glass at 500°C easily change into OH ions by thermal energy, while this chemical change does not occur in pure silica glass at 500°C. Also, germanium-doped silica fibre, in which hydrogen gas is dissolved at room temperature, shows OH ion absorption loss increase with chemical change by heat treatment at above 100°C, while pure silica core fibre shows no OH ion absorption loss increase by the same treatment.     

Temperature stability of transit time delay for a single-mode fibre in a loose tube cable

Transit time is measured as a function of temperature for a single-mode fibre installed in a loose tube cable structure. In the range from ?50°C to +60°C, the results indicate a positive linear slope of 6.7 ppm/°C, one of the lowest figures reported to date.     

InGaAsP/InP separated multiclad layer stripe geometry lasers emitting at 1.5 ?m

InGaAsP/InP separated multiclad layer stripe geometry lasers emitting at 1.5 ?m are reported. The CW threshold current at 25°C is only 82 mA and the maximum temperature where CW lasing is obtained is 65°C. The characteristic temperature of the pulsed threshold current is 60 K. The transverse mode is fundamental and the longitudinal mode is single up to 1.5 times the threshold under CW operation. A few samples operated for over 1000 h at 50°C under constant optical power operation of 5 mW/facet.     

Silicon Resonator Based 3.2 $mu$W Real Time Clock With $pm$10 ppm Frequency Accuracy

This paper presents an ultra-low power generic compensation scheme that is used to implement a real time clock based on an AlN-driven 1 MHz uncompensated silicon resonator achieving 3.2 ?W power dissipation at 1 V and ±10 ppm frequency accuracy over a 0-50°C temperature range. It relies on the combination of fractional division and frequency interpolation for coarse and fine tuning respectively. By proper calibration and application of temperature dependent corrections, any frequency below that of the uncompensated resonator can be generated yielding programmability, resonator fabrication tolerances and temperature drift compensation without requiring a PLL. To minimize the IC area, a dual oscillator temperature measurement concept based on a ring oscillator/resistor thermal sensor was implemented yielding a resolution of 0.04°C. The IC was fabricated on a 0.18 ?m 1P6M CMOS technology.     

High-temperature operation of 1.55 ?m InGaAsP double-channel buried-heterostructure lasers grown by LPE

High-temperature operation of InGaAsP double-channel buried-heterostructure (DCBH) lasers emitting at 1.55 ?m is reported. The 1.55 ?m InGaAsP DCBH lasers have threshold currents as low as 18 mA at 20°C. The threshold current temperature sensitivity between 10°C and 75°C is characterised by a T0 value of 55?66 K. Electro-optical derivative measurements show that the 1.55 ?m InGaAsP DCBH laser does not have substantial above-threshold leakage current for junction temperatures as high as 75°C. Finally, these devices were operated at temperatures as high as 110°C, the highest CW operating temperature obtained to date for a 1.55 ?m InGaAsP laser.     

Etched-coupled-cavity InGaAsP/InP lasers

A new structure for coupled-cavity lasers operating at 1.25 ?m wavelength is presented. Using chemical etching, we made a three-cavity laser from an index-guided channelled-substrate Fabry-Perot laser. It oscillates in a single longitudinal mode with a side-mode suppression ratio of 200:1 in the pumping current range of 120 mA to 220 mA. The same mode was maintained at a fixed current of 160 mA as the heat-sink temperature was varied from 9°C to 45°C. The advantages of this laser over other coupled-cavity lasers are the simplicity of fabrication, the accuracy of cavity length control, and the possibility of incorporating short-etalon sections in the coupled cavities.     

Operation of 6 GHz f.e.t. amplifier at reduced ambient temperature

An m.i.c. f.e.t. amplifier was tested at ambient temperatures varying, from 20 to ?85°C. A gain increase of 3 dB and noise figure decrease of 1.9 dB were measured over that temperature range.     

Localized hyperthermia in the treatment of malignant brain tumors using an interstitial microwave antenna array

An interstitial microwave antenna array hyperthermia (IMAAH) system was evaluated in a series of acute experiments for its ability to generate localized hyperthermic fields in the normal adult and developing dog brain. Using a single microwave antenna, the maximum diameter of heating greater than or equal to 42°C was 1.3 cm. Using four microwave antennas, temperatures greater than or equal to 42°C were obtained over a 2.5 cm cross-sectional diameter. Normal gray matter cannot be heated above 42.2°C for 60 min without causing acute damage to cortical neurons. Edema formation can occur at temperatures as low as 42°C in both gray and white matter. Disruption of myelin tracts in white matter is apparent at temperatures of 43.0-43.5°C. The IMAAH system generates significantly higher and more variable temperature distributions in virally induced experimental brain tumors than in the developing dog brain at the same power levels.     

Fabrication and performance characteristics of InGaAsP ridge-guide distributed-feedback multiquantum-well lasers

The fabrication and performance characteristics of InGaAsP ridge-guide distributed-feedback lasers with multiquantum-well active layers are reported. The lasers are 320 ?m long and have four active wells (?300 ? thick). The lasers have threshold current ?100 mA at 30°C, external differential quantum efficiency ?0.1 mW/mA/facet at 30°C and To? 60 K and can be operated in the same DFB mode up to 70°C. The measured frequency chirp is about a factor of 3 smaller than that for conventional double-heterostructure lasers. The smaller chirp should allow larger repeater spacing for high-bit-rate long-distance fibre transmission systems applications.     

Characteristics of laser-diode modules using thermally-diffused expanded core fibres

0.8 mu m band laser-diode modules have been developed for coupling to fibres with a relative refractive-index difference ( Delta ) as high as 2.3%. A coupling loss of 3.1 dB, fibre output power over 35 mW, and excellent temperature stability in the range from -10 to 60 degrees C were realised using a thermally-diffused expanded core fibre.<>     

Temperature-tunable 3.5 mu m fibre laser

Use of a Peltier element permits adjustment of fibre temperature over the range 5-41 degrees C, providing a tuning range of 30 nm for the 3.5 mu m laser. In this temperature range the laser emits nearly 1 mW at 130 mW pump power.<>     

Microthermocouple for Soft Tissue Temperature Determination

Platinum-tellurium microthermocouples with a sensing junction of approximately 1.0 ?m were constructed by vapor depositing tellurium on the exposed conical tip of a glass insulated platinum wire. The thermoelectric power, linearity, and hysteresis of the microthermocouples were determined by comparing the output of the microthermocouple with that of an iron-constantan macrothermocouple. The microthermocouple response was linear and exhibited no hysteresis over the temperature range 27-100°C. Thermoelectric power was typically 300 ?V/°C. Typical impedance was several hundred M?. The response time was less than 50 ms.     

基于MgO:PPLN晶体的中红外光参量振荡器的数值计算与分析

本文计算分析了基于准相位匹配技术的光参量振荡器的输出波长,其中振荡器所用的非线性晶体是极化周期为26-31μm(每个极化周期之间间隔为0.5μm)的MgO:PPLN晶体,晶体温度控制在40-200°C范围内,振荡器的泵浦波长为1.064μm。计算出输出波长为1.355-1.735μm(信号光范围)和2.75-4.948μm(闲频光范围),并分析了在该振荡器中极化周期、晶体温度和输出波长之间的关系。