Qinetiq Limited

Guy Neville Pearson

Michael Harris

David Bryce

David V Willetts

A coherent differential absorption lidar (DIAL) devicecomprises a transmit portionfor directing a combined light beam to a remote target and a receive portionfor receiving light returned from the remote target and for coherently mixing the received light with its associated local oscillator beam. The combined beam comprises at least two component light beams of discrete wavelengths. The device further comprises a signal correction means. The signal correction means comprising a means for extracting a portion of each component light beam from the transmit portion, a means for introducing a frequency differencebetween each extracted component light beam and its associated local oscillator beam and a means for directing the extracted beam into the receive portion. This provides an additional correction signal thereby improving device performance.

Coherent differential absorption lidar (dial)

A coherent laser radar (lidar) device is described. The device has a transmitter portion that comprises a single wavelength laser source, a conversion means (such as an electro-optic modulator) for producing a combined light beam that comprises at least two component light beams of discrete wavelength from the output of said single wavelength laser source, and transmit optics to direct the combined light beam to a remote target. Each component light beam of the combined light beam traverses the same optical path from the single wavelength laser source to the transmit optics. The device is used to make differential absorption measurements.

Laser radar apparatus having multiple output wavelengths

An optical transmission system includes an optical source such as a laser having an optical output, this optical output being modulated such that it has periods of operation having a first set of characteristics interspersed with periods of operation having a second set of characteristics. The output is then split into at least two signals, and one of the signals delayed with respect to the other signal before the two are mixed, such that a portion of the modulated optical output having the first set of characteristics in one of the signals corresponds with a portion of the modulated optical output having the second set of characteristics of another of the signals. This allows a single optical source to provide to a receiver a local oscillator signal simultaneously with a data carrying signal. The system is particularly suitable for lidar applications, including gas sensing, but also has utility in data communications systems.

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Malvern, United Kingdom

Guy Neville Pearson