Applications of optical fibers for communication, signal processing and acoustics

光纤网络构成了互联网和语音通信的主干。光纤传输速度从80年代的几Mb/s稳步增长到最近的Tb/s，从而实现了更快的互联网服务。传输速度和范围主要受到光纤系统中传播损伤的限制。本研究计划主要针对光纤中的线性与非线性传输损伤，以及如何减轻这些损伤，以改善其性能。我们建议发展快速电均衡器来补偿光纤传输所造成的线性和非线性损伤。还将研究在光纤链路末端引入光学反向传播模块的可能性，该模块可以在真实的时间内补偿光纤非线性损伤。该模块可以在宽频带上补偿非线性，因此，它与波分复用系统兼容。 声激光是一种高相干的声波源。就像激光已经彻底改变了光子学一样，人们预计声学激光也会对声学做同样的事情。利用光纤中受激布里渊散射过程在光纤中产生声波，并在两侧放置声镜提供反馈，从而构成声激光器。使用声激光的超声成像系统能够分辨即使是最强大的显微镜也可能错过的物体。我们将探索用光纤构造声激光器的可能性。 在许多数字信号处理（DSP）应用中，需要对离散傅里叶变换（DFT）进行快速求值。在本研究计画中，我们提出使用时间透镜为基础的2-F系统来实现光子DFT。基于时间透镜的2-F系统可以使用光纤和相位调制器来实现。来自几台计算机的信号可以组合成一个复合信号，该复合信号的DFT可以用光学方法计算，并且在光电转换（O/E）和解复用之后，信号的所需DFT将被发送到计算机。 光子DFT的优点是它具有很大的带宽，因此可以同时计算来自多台计算机的信号的DFT。

A fiber-optic network forms a backbone of the internet and voice traffic. Fiber-optic transmission speed has steadily increased from several Mb/s in 80s to Tb/s recently, enabling faster internet services. The transmission speed and reach are mainly limited by the propagation impairments in fiber-optic systems. This research proposal focuses on the study of linear and nonlinear propagation impairmens in optical fibers and how to mitigate them so that the performance can be improved. We propose to develop fast electrical equalizers to compensate the linear and nonlinear impairments due to fiber propagation. The possibility of introducing an optical back propagation module at the end of the fiber-optic link that could compensate for fiber nonlinear impairments in real time will also be investigated. This module could compensate for nonlinearities over a wide band and therefore, it is compatible with wavelength division multiplexed systems. Acoustic laser is a highly coherent source of acoustic waves. Just like lasers have revolutionized photonics, it is expected that acoustic lasers would do the same thing for acoustics. Acoustic waves are generated in optical fibers by the process of stimulated Brillouin scattering in fibers and the acoustic mirrors placed on both sides provide the feedback so that acoustic laser can be constructed. The ultrasound imaging system that uses acoustic laser is capable of resolving objects that even the most powerful microscopes could miss. We will explore the possibility of constructing acoustic laser using optical fibers. The fast evaluation of discrete Fourier transform (DFT) is required in many digital signal processing (DSP) applications. In this research proposal, we propose to use the time lens based 2-F system for the realization of photonic DFT. A time lens based 2-F system can be implemented using optical fibers and phase modulators. The signals coming from several computers can be combined to form a composite signal whose DFT can be computed optically and after the optical to electrical conversion (O/E) and demultiplexing, the desired DFT of the signals will be transmitted to the computers. The advantage of photonic DFT is that it has a large bandwidth and therefore, it can compute the DFT of the the signals coming from many computers simultaneously.