The technical principle of optical fiber delay lines
The working principle of optical fiber delay lines is based on the characteristic that there is a delay in the transmission of light in optical fibers. When light propagates in optical fibers, its propagation speed is relatively fixed. By changing the path length of light transmission in optical fibers, the delay time of optical signals can be controlled. Simply put, when optical signals are transmitted over longer optical fibers, the time required is longer, thereby achieving the purpose of delaying the optical signals.
There are various common implementation methods for optical fiber delay lines, such as mechanical, electronic and all-optical types. Mechanical optical fiber delay lines stretch or contract optical fibers through mechanical devices to change the transmission path length of optical signals. The electronic optical fiber delay line modulates the phase of the optical signal with the help of electronically controlled optical devices, such as electro-optic modulators, etc., to indirectly achieve the delay effect. All-optical fiber delay lines utilize the nonlinear optical effects of optical fibers to complete the delay processing of optical signals within the optical domain, without the need for an electro-optical conversion process. They have the advantages of high speed and wide bandwidth.
Core advantages: High precision and flexibility
Optical fiber delay lines have significant advantages of high precision and high flexibility. In terms of accuracy, due to the stable transmission characteristics of optical fibers, high-precision delay control at the picosecond or even femtosecond level can be achieved. This high-precision delay control capability enables optical fiber delay lines to play a significant role in optical measurement fields with extremely high requirements for time accuracy. For instance, in the time measurement of femtosecond laser pulses, optical fiber delay lines can precisely adjust the arrival time of the optical signal, helping researchers accurately obtain the time characteristics of the laser pulse.
In terms of flexibility, optical fiber delay lines can flexibly adjust the delay time according to actual needs by changing the length of the optical fiber or adopting an adjustable delay structure. Whether it is short-distance nanosecond-level latency or long-distance millisecond-level latency, it can be easily achieved. In addition, the soft and flexible nature of optical fibers enables them to adapt to various complex application environments and facilitate integration into different optical systems.
Diverse application fields
(1) Optical communication field
In optical communication systems, optical fiber delay lines are used for the synchronization and delay compensation of optical signals. With the development of high-speed optical communication technologies, such as coherent optical communication systems, there is a time difference in signal transmission between different optical paths, which will affect the demodulation and processing of signals. Precise delay adjustment of optical signals through optical fiber delay lines can achieve the synchronization of multiple optical signals, improving the stability and transmission efficiency of the communication system. In addition, in the signal caching and routing switching of optical networks, optical fiber delay lines also play an important role, helping to optimize network performance and reduce signal transmission delay.
(2) Optical measurement field
In optical measurement experiments such as interferometry and spectral analysis, optical fiber delay lines are indispensable tools. In interference measurement devices such as Michelson interferometers, the introduction of optical fiber delay lines can change the optical path difference of the interference arm, precisely control the movement of interference fringes, and thereby achieve high-precision measurement of physical quantities such as minute displacements and strains. In spectral analysis, by adjusting the arrival time of the optical signal through the optical fiber delay line, time-resolved measurement of the spectral signal can be carried out to obtain more abundant spectral information.
(3) Lidar field
The lidar system measures the distance and position information of the target by using the reflection time of the laser signal. Fiber optic delay lines are used in lidar to simulate the distance delay of the target, achieving precise calibration and testing of the radar system. By setting different delay times and simulating the target reflection signals at different distances, it helps engineers evaluate the performance indicators of the lidar, optimize system parameters, and improve the ranging accuracy and resolution of the lidar.
Fiber delay lines, as a key technology for precise control of optical signals, play an irreplaceable role in multiple important fields such as optical communication, optical measurement, and lidar, thanks to their unique technical principles, high precision, and flexibility. With the continuous advancement of optical technology, optical fiber delay lines will also keep innovating and developing, expanding their applications in more cutting-edge fields, and providing strong support for the progress of optical technology and the development of related industries.