寬頻光射頻頻譜分析儀

Abstract

摘要

隨著光通訊系統的傳輸速率的增加, 傳統量測光通訊信號的方法漸漸地顯得局促了. 由於這些傳統的方法是將光通訊訊號先轉為電信號, 再由電的分析儀器, 來分析, 所以, 受到了光轉電以及分析儀器電子電路頻寬的限制.

其中, 信號的射頻頻譜是一個很重要且基本的量測. 一般電的射頻頻譜分析儀, 其頻寬限制約在50GHz, 對於40Gbps的光通訊信號而言, 以顯不足. 為此, Dorrer博士和Maywar博士在2003年提出了一個全光量測光信號射頻頻譜的方法. 這是一個簡單而且對於往後高傳輸速率的光通訊系統深具潛力的射頻頻譜量測方法. 我們對它非常感興趣, 因此依循Dorrer博士和Maywar博士的方法, 架設了如此一個光射頻頻譜分析儀.

並且, 仔細討論了它的工作原理以及相關的理論, 包括模擬量測的頻譜, 以之與實驗的結果比較, 並預測此方法因為信號光能量過大造成的誤差, 找出較適合的操作.

除此之外, 我們以實驗以及理論模擬預測了所架的光射頻頻譜分析儀其具有的頻寬. 在不考慮頻譜展開以及信號重疊的情況下, 它具有約750GH的頻寬, 比電的射頻頻譜分析儀高出了一個數量級. 最後, 我們討論了此種全光光射頻頻譜分析儀的主要缺點—測量解析度的問題, 並建議了幾種改進的方法.

ABSTRACT

The conventional approach for measuring the optical communication signals is too restricted when the higher optical communication systems come. These conventional approaches are to convert the optical signal into electrical signal first and then do analysis by electrical instruments, so they are restricted by the optical-to-electrical conversion and electrical circuits in bandwidth. One of important and basic measurements for communication signals is to measure its RF spectrum. The largest bandwidth for general electrical RF spectrum analyzer is around 50GHz, which is insufficient for the measurement of 40Gbps optical communication signals. Therefore Dr. Dorrer and Dr. Maywar proposed an all optical approach for measuring the RF spectrum of optical signals in 2003. It is a simple method and has large potential for high bit rate optical communication systems. We have great interest in this all optical approach, so we set build up an optical RF spectrum analyzer based on the approach proposed by Dr. Dorrer and Dr. Maywar.

Furthermore we discuss its working principle and the related theories including simulating the spectrum that we prepare to measure and compare it with the practical measured results. And predict the distortion due to too large signal power in this approach and find a suitable signal power in operation. Beside those, we still predict the achievable bandwidth of the optical RF spectrum analyzer with experiment and simulation. It has the largest bandwidth around 750GHz in the case without considering spectral extending and signal overlapping.

Finally we discuss the major drawback of this approach—bad measuring resolution and suggest several possible methods for enhancing the measuring resolution.