Coherent light generators – Particular beam control device – Optical output stabilization
Patent
1984-11-09
1990-09-04
Sikes, William L.
Coherent light generators
Particular beam control device
Optical output stabilization
372 38, H01S 313
Patent
active
049550292
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
The invention relates to the regulation of laser diodes operating continuously and it finds an important although not exclusive application in the field of optical fiber digital transmissions.
It is known that laser diodes are widely used for optical fiber transmission, in particular because they are capable of operating at much higher frequencies than light emitting diodes. But on the other hand these laser diodes have the disadvantage of presenting considerable variations of the light power emitted in response to the small variation of the current with respect to the threshold value. Now, this threshold value presents appreciable variations which are either reversible, as a function of the temperature more especially, or irreversible following aging more particularly.
To palliate the effects of these variations, it is necessary to provide regulation of the output light power. Processes are already known for regulating the light power emitted by a laser diode under continuous operating conditions, in which an electric signal representative of said light power is compared with an electric reference signal corresponding to a reference power for elaborating an error signal, and the operating conditions of the laser diode are automatically modified as a function of said signal.
Usually, it is the electric current supplying the laser diode which is controlled by a feedback loop whose input value is formed by the difference between the measured output light power and a reference power.
It is frequently necessary to add to this servo control a temperature regulation for present laser diodes must operate at a temperature at most not much higher than the normal ambient temperature. High temperatures in fact accelerate the aging and increase the risk of destruction, whereas on the contrary lowering of the temperature during operation increases the lifespan. Another reason which makes a temperature regulation frequently necessary is the need to remove the heat released at the junction of the laser diode. This temperature regulation is generally effected by cooling with an active element, such as a Peltier effect element, controlled by a second feedback loop whose input signal is formed by the difference between the measured temperature of the laser and the reference temperature.
Different reasons, which will be given in detail further on, cause this solution to be unsatisfactory. In particular, this double regulation requires a larger number of components and it suffers from a defect in its very principle: to maintain the light power emitted, during aging, the supply current must be increased, which causes an increase in heating and in the power consumed by the Peltier effect element, resulting in an increase in the overall power consumed. In addition, it is difficult to measure the temperature of the junction of the laser diode, so that the temperature measured is that of the base of the diode, to which a thermistor is fixed. The temperature differences which exist between the base and the junction will increase gradually with increases of electric current during aging, so that, for a fixed reference temperature, the temperature of the junction increases, which further accelerates aging.
It is an object of the invention to provide an improved regulation process and device. It is a more specific object of the invention to provide a device which is simple in construction and which eliminates the above mentioned positive reaction phenomena.
To this end, the invention uses the fact that the threshold current of a laser diode increases with the temperature according to a law which is approximately exponential, and it proposes more especially a process of the above defined kind which is characterized in that the heat flow extracted from the laser diode is controlled so as to cancel out the error signal while feeding the laser diode with constant electric current.
The invention also proposes a regulation device for implementing the above defined process. This device comprises a pho
REFERENCES:
patent: Re31969 (1985-08-01), Sell
patent: 3395367 (1968-07-01), Bell et al.
patent: 3464024 (1969-08-01), Bell et al.
patent: 3628173 (1971-12-01), Danielmeyer
patent: 3831108 (1974-08-01), LeFloch
patent: 3986117 (1976-10-01), Fry et al.
patent: 4115828 (1978-09-01), Rowe et al.
patent: 4181899 (1980-01-01), Liu
patent: 4181901 (1980-01-01), Heyke
patent: 4309671 (1982-01-01), Malyon
patent: 4501022 (1985-02-01), Oswald
Lecoy Pierre
Wilbrod Jean-Hubert
Sikes William L.
Wise Robert E.
LandOfFree
Process and device for regulating the light power of laser diode does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process and device for regulating the light power of laser diode, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process and device for regulating the light power of laser diode will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-447006