Abstract: An optical power meter including a photodiode having a surface for receiving a beam of light, a thermo-electric cooler for maintaining the photodiode at a predetermined temperature, and a current monitor for measuring a drive current passing through the thermo-electric cooler allows dark current drift arising from a varying thermal gradient across the active region of the photodiode to be corrected, thus improving stability of the optical power meter. More specifically, by monitoring the TEC drive current, and applying a correction factor to the optical power readings, the stability of optical power readings is improved by an order of magnitude.

Abstract: An optical power meter including a photodiode having a surface for receiving a beam of light, a thermo-electric cooler for maintaining the photodiode at a predetermined temperature, and a current monitor for measuring a drive current passing through the thermo-electric cooler allows dark current drift arising from a varying thermal gradient across the active region of the photodiode to be corrected, thus improving stability of the optical power meter. More specifically, by monitoring the TEC drive current, and applying a correction factor to the optical power readings, the stability of optical power readings is improved by an order of magnitude.

Abstract: In "C" dolly systems, it is conventional to provide a resistance to steer of approximately 0.3 G in order to improve the steering thereof particularly in an evasive action and to decrease the tendency of high speed off tracking. The higher this resistance to steer, the better the high speed off tracking characteristics are. However, high resistance although relatively satisfactory at high speeds, at relatively low speeds below approximately 30 miles an hour, results in the creation of severe and undue stresses and forces in the dolly and hitch structures particularly during relatively tight turning maneuvers. The present invention comprises a two phase control system. The speed of the vehicle is sensed continuously and when the speed is below approximately 30 mph (approximately 50 kph) the steering axle of the dolly is free to steer under the control of the axle steering dampening system but above 30 mph (50 kph), the axle is locked thus giving the maximum resistance to steer.