Abstract:
In a laser apparatus for measuring the velocity of a fluid, a measurement laser light beam (M) fed into the fluid and scattered by a particle within the fluid is made to interfere with a reference laser light beam (R) to generate an interference signal based on the velocity of the particle; the apparatus comprises a low-coherence laser source (10) and interferometric means (11, 12) which split the light beam of the laser source (10) into the stated reference light beam (R) and measurement light beam (M), and cause the reference light beam (R) derived from the laser source (10) to interfere with the backscattered component resulting from the scattering of the measurement light beam (M).
Abstract:
A filter for an optical fibre temperature sensor comprising at least one first and one second optical filter for filtering an optical pulse reflected by said optical fibre, characterised in that said at least one first and one second optical filter comprise standard commercial filters complying with ITU specifications, said optical pulse lying within the range from 1570 nm to 1580 nm.
Abstract:
An optical fibre temperature sensor comprising: an optical pulse generator; an optical fibre into which said optical pulses are fed; an optical receiver to receive said optical pulses reflected by said optical fibre and to convert them into an electrical signal; a processor which receives said electrical signal and determines the temperature along said optical fibre; said optical receiver comprising a first filter and a second filter to filter said optical pulse reflected by said optical fibre, characterised in that said first and said second filters filter two adjacent portions of anti-Stokes optical signals or of Stokes optical signals
Abstract:
An optical switching system includes a two-dimensional arrangement of a plurality of switching elements. Each switching element includes an optical guiding structure which includes two pairs of waveguides; a driving arrangement for individually moving the switching elements between at least a first and a second position; and a first and a second input and a second output. When a generic switching element is moved in the first position, the first pair of waveguides connects a first input with a first output, and a second input with a second output; when a generic switching element is moved in the second position, the second pair of waveguides connects the first input with the second output, and the second input with the first output. In a first embodiment, the waveguides are provided on a disc shaped carrier and lie in the same plane, which disc is rotated. In a second embodiment, the two pairs of waveguides lie in different planes and the waveguide carrier plate is moved up and down for switching.
Abstract:
A wavelength converter device is provided for generating a converted radiation at frequency ωg through interaction between at least one signal radiation at frequency ωs and at least one pump radiation at frequency ωp, including an input for the at least one signal radiation at frequency ωs, a pump light source for generating the at least one pump radiation at frequency ωp, an output for taking out the converted radiation at frequency ωg, a structure for transmitting the signal radiation, including two optical resonators having a non-linear material, having an optical length of at least 40*λ/2, λ being the wavelength of the pump radiation, and resonating at the pump, signal and converted frequencies ωp, ωs and ωg, wherein by propagating through the structure, the pump and signal radiation generate the converted radiation by non-linear interaction within the optical resonators.
Abstract:
Wavelength converter device for generating a converted radiation at frequency Ωg through interaction between at least one signal radiation at frequency Ωg and at least one pump radiation at frequency Ωg, with an input for the at least one signal radiation at frequency Ωg; a pump light source for generating the at least one pump radiation at frequency Ωg, an output for taking out the converted radiation at frequency Ωg, a structure for transmitting the signal radiation, the structure including one optical resonator having a non-linear material, having an optical length of at least 40*η/2, wavelength η being the wavelength of the pump radiation, and resonating at the pump, signal and converted frequencies Ωp, Ωs, and Ωg. The structure has a further optical resonator coupled in series to the optical resonator, the further optical resonator having a non-linear material, having an optical length of at least 40*η/2, wherein η is the wavelength of the pump radiation, and resonating at the pump, signal and converted Ωp, Ωs and Ωg, wherein by propagating through the structure, the pump and signal radiation generate the converted radiation by non-linear interaction within the optical resonators.
Abstract:
An optical device for providing threshold and comparison functions. The device comprises first and second SOA's having respective first and second propagation paths along which the first and second optical signals, input as signals Pin1(&lgr;1) and Pin2(&lgr;2) travel in first and second forward directions. A feedback path is provided using couplers to interconnect the outputs of the SOA's. As a result, a portion of the optical signals output from each SOA is supplied backwards into the output of the other SOA as feedback optical control signals Pfeedback1(&lgr;1) and Pfeedback2(&lgr;2). The feedback optical control signals modulate the gain of the forwards travelling optical signals by cross gain modulation (XGM). In contrast to prior art devices, the optical control signal is supplied backwards into the SOA's in a counter-propagating configuration. This allows much shorter feedback path lengths to be achieved in comparison to what is possible with prior art co-propagating configurations. Consequently, much higher bit rates can be achieved. The device may also be implemented in planar waveguide technology.
Abstract:
An optical selector for an asynchronous transfer mode (ATM) optical network, the said selector being capable of selecting ATM cells of bits having a frequency of arrival f less than or equal to a predetermined frequency (PCR), the said optical selector comprising: an input having a first device capable of blocking the entry of bits; an output having a second device capable of permitting the outflow of bits; an ATM cell recognition unit constructed in such a way that it recognizes the headers of ATM cells and connected to the said input and to the said output for the transit of bits from the said input to the said output; and an optical decision unit connected operationally to the said first device, to the said second device and the said ATM cell recognition unit.
Abstract:
An optical device having a first input for at least one input optical signal having a random state of polarization and a first optical element capable of dividing, in space, the input optical signal into a pair of optical signals which are substantially parallel and have a predetermined state of polarization perpendicular to each another. The optical device also having a first crystal element for propagation, in free space, of at least the pair of optical signals coming from the first optical element, and the first crystal element being devoid of internal separation planes, and having electro-optical properties and being associated with electrodes so as to apply a voltage in a direction substantially perpendicular to the direction of propagation, along the first crystal element, of the at least one pair of optical signals. The optical device also having an optical control element for supplying at least one optical control beam, having a predetermined power, to the first crystal element, the at least one optical control beam being superimposed on the at least one pair of optical signals and having a direction of propagation which along the first crystal element is substantially perpendicular to the direction of application of the voltage, the at least one optical control beam being capable of causing to rotate through a predetermined angle the state of polarization of the at least one pair of optical signals in the first crystal element. The optical device also having a second optical element capable of combining the at least one pair of optical signals coming from the first crystal element in a single output signal and a first output for the output signal.
Abstract:
The detector comprises an electro-optical section for the signal analysis, a transmission fibre-optic, a fibre-optic coupling of high immunity to environmental noise, and a fibre-optic sensor terminating in a reflecting element. It can be provided in either homodyne or heterodyne version (phase or frequency modulation). This latter version has the advantage of detecting phase modulations exceeding 2.pi. radians. Both the versions have the advantage of enabling measurements to be made which are not influenced by environmental disturbances affecting the transmission fibre-optic.