A Low-Frequency Tone Sweep Method for In-Service Fault Location in Subcarrier Multiplexed Optical Fiber Networks

Abstract

We demonstrate an optical fiber fault location method based on the frequency response of the modulated fiber optical backscattered signal in a steady state low-frequency step regime. Careful calibration and measurement allows for the reconstruction of the fiber transfer function, which, associated to its mathematical model, is capable of extracting the fiber characteristics. The technique is capable of identifying non-reflective fault events in an optical fiber link and is perfectly compatible with previous methods that focus on the reflective events. The fact that the recuperation of the complex signal is performed in the frequency domain and not via a Fourier Transform enables the measurements to overcome the spatial resolution limitation of Fourier Transform incoherent-OFDR measurements even with frequency sweep ranges down to 100-100000 Hz. This result is backed up by a less than 10 meters difference in fault location when compared to standard OTDR measurements.

Single-Ended In-Service Hybrid Monitoring of Fiber-Extended Copper Lines

“…Once again, the fault was induced by bending the fiber, but a defective connector was spliced to the fiber end so we could assess the response of the system to a reflective event. As discussed in [9], reflective events have a negative effect over measurements of the Rayleigh scattering signal within a RF subcarrier since its amplitude is not diminished as the frequency rises, unlike the Rayleigh scattered signal. If, therefore, the reflection from a discrete reflective event is too strong, the signal of interest is buried underneath the detection margin.…”

“…(1), non-reflective fiber faults, such as the ones resulting from fiber bending, are to be considered in the second parcel. It is shown in [9] that, in a multiple non-reflective fault scenario, the integral will be split into multiple terms that follow the same form with a parameter that depends on the distance of the fiber fault. The complex representation of the generic term resulting from the integration in this multiple fault scenario is presented in Eq.…”

“…with I R ⊆ I, meaning that the set of reflective events is a subset of all the events but not necessarily equal to the latter [9].…”

Full Optical Fiber Link Characterization With the BSS-Lasso

“…Following this rationale, a novel transparent and cost-effective reflectometry-based technique has been recently developed [12]. Due to its characteristics, the technique will be henceforth dubbed as Baseband Subcarrier Sweep (BSS).…”

Automatic High-Dynamic and High-Resolution Photon Counting Otdr for Optical Fiber Network Monitoring

“…The OFDR technique uses continuous wave light source which is swept continuously in frequency. The sweep can be done by varying the optical carrier, coherent-OFDR, or its modulation envelope, incoherent-OFDR [32,39,40]. The coherent measurement consists of analyzing the heterodyne beat between a fixed reference reflection and the backscattered signal.…”