Abstract:
A temperature measurement circuit includes a switched sensing circuit and measures alternately a characteristic of the switched sensing circuit that depends on a thermistor and on a reference resistor, using common electrical components, including a multi-pole switch. The resistance of the thermistor varies with temperature over a known temperature range, and the resistance of the reference resistor remains substantially fixed over the range of temperatures being measured. The temperature measurement circuit also includes a detection circuit. The switched sensing circuit responds to a temperature to be measured, and also responds to a detection circuit sitich control signal. It provides switched sensing circuit signals containing information about the characteristic of the sensing circuit with the thermistor and the reference resistor, in turn, switched into the circuit. The detection circuit provides the detection circuit switch control signal, and responds to the switched sensing circuit signals. It provides a detection circuit signal containing information about the temperature to be measured. In one embodiment, the common set of electrical components includes a capacitor connected in series with a multi-pole switch in the switched sensing circuit and a comparator in the detection circuit. In another embodiment, the switched sensing circuit is a (switched) resistance-tunable oscillating circuit.
Abstract:
An optical spectrum analyzer (OSA) (10) sequentially or selectively samples (or filters) a spectral band(s) (11) of light from a broadband optical input signal (12) and measures predetermined optical parameters of the optical signal (e.g., spectral profile) of the input light (12). The OSA (10) is a free-space optical device that includes a collimator assembly (15), a diffraction grating (20) and a mirror (22). A launch pigtail emits into free space the input signal through the collimator assembly (15) and onto the diffraction grating (20), which separates or spreads spatially the collimated input light, and reflects the dispersed light onto the mirror (22). A N4 plate (26) is disposed between the mirror 22 and the diffraction grating (20). The mirror reflects the separated light back through the N4 plate (26) to the diffraction grating (20), which reflects the light back through the collimating lens (18). The lens (18) focuses spectral bands of light (η 1- η N ) at different focal points in space. One of the spectral bands (11) is focused onto a receive pigtail (28), which then propagates to a photodetector (30). A pivoting mechanism (34) pivots the diffraction grating 20 or mirror (22) about a pivot point (36) to sequentially or selectively focus each spectral band (11) to the receive pigtail (28). A position sensor (42) detects the displacement of the diffraction grating (24) or mirror.
Abstract:
A method and corresponding apparatus for determining the centroid (V c ) of a waveform signal being sampled at a set of parameter values (V i , i=1, ..., n) yielding a corresponding set of sampled amplitudes (A i , i=1, ..., n), each parameter value and corresponding amplitude forming a sampled point (V i , A i ), the method including the steps of: selecting an amplitude at which to create an interpolated point; interpolating a first parameter value corresponding to the amplitude selected in the step of selecting an amplitude; and performing a centroid calculation using only the sampled points with an amplitude greater than a predetermined threshold. The waveform is sometimes sampled in the presence of background noise, and the method sometimes also includes: estimating the background (B i ) for each value in the set of parameter values at which sampling is performed; and reducing the amplitude (A i ) of each sampled amplitude by the background (B i ) so estimated.