Study Of Temperature-controlled Fiber Delay Line With Continuously Tunable Large Dynamic Range

Optical fiber delay line is widely used in the field of electronic counter-measurement, time and frequency transfer system, phased array radar, optical signal processing and so on. Comparing with the electrical delay line, optical fiber delay line has many advantages of high working frequency, great time delay dynamic range, large time-bandwidth product, immunity to electromagnetic interference, etc. There always exists large time jitter in long-distance signal transmission systems because of temperature vibration, crustal movement, and humanity disturbance. It is significantly needed to continuously compensate the time jitter in a stable transmission system by use of a tunable optical fiber delay line with a large dynamic range.The discontinuous fiber delay line is easily realized, of which the dynamic range is usually limited to hundreds of picoseconds (ps). However, for long-distance transmission systems, the fiber delay line needs to have large dynamic range and be continuously tunable. Up to date, the continuous fiber delay line with nanoseconds (ns) dynamic range was mainly realized by a temperature-controlled container as demonstrated in literatures.In this thesis, a temperature-controlled fiber delay line is designed and implemented with a dynamic range as large as 7.3ns and a temperature range of 40℃, which is larger than the results reported by NASA and NICT. It is then used to compensate the time jitter existing in the fiber frequency transfer system. The experimental result matches well the simulated PID control scheme done by Matlab. The compensation accuracy reaches 5ps under the triangle wave noise with 200ps range and 2.5ps/s speed and becomes to be 0.5ps under the environmental noise.First, it is analyzed the relation between the achievable time delay of the temperature-controlled fiber delay line and the heat-conducting power as well as the electro-caloric effect of semiconductor coolers. A method is presented to analyze and determine the important parameters of the optical fiber delay line, such as the temperature range, the semiconductor cooling power, and the heat-insulated container structure. A driver circuit is designed and implemented.Second, the heat transfer model of the temperature-controlled fiber delay line is demonstrated. The heat transfer process between each neighboring two of the semiconductor cooler, the heat-conducting medium, the fiber jacket and the fiber core is simulated. The time delay variation behavior under cooling and heating environment is obtained.Finally, the performance of temperature-controlled optical fiber delay line to compensate the time jitter in the frequency transfer system is verified. The dynamic range and variation rate of the compensation is experimentally characterized. Besides, the heating/cooling characteristics, the relation of the temperature dynamic range and the heating/cooling power, and the effect of different parts in the optical delay line are studied, respectively. Besides, the performance with and without heat-insulated container are compared.