Abstract: A laser assembly including a silicon base and method are provided for assembling lasers on a platform in a reliable, low cost process that is suitable for high volume production. The platform can be a monolithic silicon base which has high thermal conductivity, a low coefficient of thermal expansion, and whose features can be formed with close tolerances in a low cost, reliable manner. Materials with similar coefficients of thermal expansion are used in order to maintain alignment during unexpected heating and cooling. Furthermore, a method is described that substantially eliminates the need for adhesives to bond laser components to a platform. The resultant laser can be very robust, stable, and can provide reliable operation over extended time periods.

Abstract: Optical fiber measuring systems using an interferometer are disclosed. The measuring range of the system are extended by the use two wavelengths of radiation during the measurement. The phases of the light at each wavelength may be compared, or the radiation of one wavelength may be used to calibrate the radiation of the other wavelength.

Abstract: A flowmeter for measuring the velocity of fluid flow by monitoring the vortex shedding frequency of the fluid flow comprises a single mode optical fibre sensing element (1) for detecting vortex shedding and utilizes interferometric techniques for producing an electrical output signal corresponding to the vortex shedding frequency. The sensing element (1) comprises at least part of the signal arm (2) of an interferometer (3) which also includes means (12) for deriving a reference signal from the illuminating light source (4). The flow induced oscillation of the sensing element (1) caused by vortex shedding produces modulations of the interferometer output which is monitored by a photodetector (14) which, in turn, produces a modulated electrical output signal which can be processed by a signal processing system (16-19) to identify the vortex shedding frequency and, hence, produce a measurement of the flow velocity.