High-accuracy optical frequency domain reflectometry by single-sweep frequency-averaging

摘要

With fine spatial resolution, high sensitivity and broad dynamic range, optical frequency domain reflectometry (OFDR) has been applied to fiber deviceetwork diagnoses and optical coherence tomography. In OFDR, interference between random reflections/backscattering in the fiber under test creates a noise-like effect called fading noise, which can be reduced by measuring at different wavelengths/frequencies and taking the average. However, the typical process to realize this averaging consists of shifting the central frequency of the light source in multiple sweeps, requiring a long measurement time. In this report, we proposed a technique of single-sweep frequency averaging, which consists of averaging data acquired in a single sweep. Its efficiency was verified in a fiber laser based system with -110 dB noise floor and the measurement time including data processing was only a few seconds.%高空間分解能，高感度と広ダイナミックレンジをもつ光周波数領域リフレクトメトリ（OFDR）は光ファイバデバイス・ネットワークの診断や光コヒーレントトモグラフィ（OCT）に応用されてきた．OFDRにおいて，被測定ファイバ内のランダムな後方散乱と多重反射が干渉してフェイディングノイズというノイズのような現象を起こし，このノイズを低減させるために異なる中心周波数を用いた測定結果を平均する手法がある．但し，これを実現する一般的な方法は光源の複数回の周波数掃引を必要とし，測定時間が長くなってしまう．本研究では，単一の光周波数掃引で得られたデータを平均する手法を提案し，光ファイバレーザーを用いた実験系でその性能を確認した．このシステムのノイズフロアは-110dBで，データ処理を含む測定時間は数秒以内に抑えることができた．