We propose a technique using the vibration coupling factor analysis to automate telecommunication facility position mapping on DAS traces. The proposed method is demonstrated to have accuracy of about 6m.

We propose the simultaneous monitoring of 8-fiber routes by means of high-speed switching for time-sharing frequency division multiplexed distributed acoustic sensing (TS-FDM- DAS). We demonstrate traffic monitoring in the field area by our TS-FDM-DAS proposal.

We measure a field-deployed telecommunication fiber cable before and after repairing detachment from hanger by using multi-frequency Φ-OTDR DAS, showing possibility of detecting the abnormality based on change of vibration patterns for the first time.

Distributed acoustic sensing (DAS) using optical fiber cables, widely deployed for communications, can capture various information on the surrounding environment. Phase-sensitive optical time-domain reflectometry (Phi-OTDR) DAS is suitable for sensing deployed cables because Phi-OTDR has long measurement distances. However, a simple Phi-OTDR setup suffers from interference fading, in which sensitivity degradation occurs at many points. Multi-frequency Phi-OTDR is a practical solution that can remove the sensitivity degradation points effectively by averaging the signals of multi-frequency pulses. The method used to average multi-frequency signals affects the total measurement performance, including the sensitivity and the measurable vibration amplitude range. While vector-based averaging on the IQ plane is a powerful method in terms of sensitivity, calculating accurate vibration waveforms becomes difficult when vibrations become strong (> sub-mu epsilon). Consequently, large-scale vibration patterns are not accurately visualized, limiting potential applications. In this work, we develop a vector-based averaging method that can resolve this issue. We clarify that the known problem of the difference in phase response to strain change between multiplexed frequencies is the key matter causing the issue. To address this discrepancy, we propose a dynamically updated vector-based averaging method, enabling us to monitor strong vibrations. In the proposed method, parameters used in vector-based averaging-rotation angles and reference frequencies-that are fixed in the conventional method are updated over time in accordance with the fiber state. We demonstrate the effectiveness of the proposed method in both laboratory and field environments. We successfully visualize patterns of large-scale vibrations experienced by field-deployed communication cables, such as those caused by vehicle movements and wind blowing.

We propose vector-based multi-position multi-frequency phase averaging in multi-frequency φ-OTDR to measure large-scale vibrations over sub-με with high precision while balancing system simplicity and spatial resolution. We detect more correct vibration patterns on real-field network.

We propose an extended metro/access integrated network architecture comprising two layers with fiber-based and wavelength-based cross-connects for fiber-path and end-to-end wavelength connection services, respectively. Simultaneous demonstration of 100-Gbit/s dense wavelength-division-multiplexing transmission and field-access fiber sensing without interference confirms its effectiveness.

We develop highly sensitive and accurate multi-frequency Φ-OTDR distributed acoustic sensing suitable for measuring large-scale vibrations over sub-με amplitudes. We capture more correct detailed vibration patterns on both underground and aerial sections of an optical fibre network deployed for telecommunication services in a real-field trial.

We observe the waveform distortion in FDM-based sampling-rate-enhanced Φ -OTDR with pulse compression for the first time. We demonstrate that our complementary frequency approach is compatible and effective in suppressing the waveform distortion.

We present a field demonstration of distributed vibration sensing with FDM-Φ-OTDR in a deployed optical fiber cable network. Additionally, we propose and verify a vibration trace analysis technique that can localize telecommunication facilities.

Impulse responses of 2-mode fibres are measured by a method based on linear optical sampling with newly developed amplitude averaging technique with phase noise compensation. The intermodal coupling is observed with 10-ps time resolution and 80 dB dynamic range.

This paper introduces an in-service line monitoring technique that can locate a fault in branched optical fibers in passive optical networks (PONs) from a central office. This technique can upgrade the conventional optical fiber line testing and monitoring system. To distinguish a backscattered signal from each branched PON fiber, we employ the fibers with individually assigned Brillouin frequency shifts (BFSs) fibers as drop cables and a 1650-nm Brillouin optical time-domain reflectometer (B-OTDR) instead of the OTDR used in the conventional testing system. This paper describes the design of the BFS taking the outside plant environment into consideration, and discusses the performance of the proposed testing system. We also demonstrate an experimental measurement that locates a fault in a branching fiber after a 1 × 8 optical splitter, and in-service line monitoring for gigabit Ethernet PON (GE-PON) transmission systems.

We present a bandwidth reduced BOTDR realized by using reference Brillouin scattering as a local light. Temperature distribution sensing is successfully demonstrated by compensating for the temperature variation in the reference fiber.

We propose a method that down-converts the electrical bandwidth for Brillouin frequency shift sensors with heterodyne detection without the need for any expensive instruments or a complicated system. We discuss the power and coherency of the stimulated Brillouin scattering light required for the reference fiber. We confirm that the frequency bandwidth measured with the proposed method is much lower (0.2 GHz) than that measurable with conventional heterodyne detection (11 GHz). Moreover, the proposed method can measure the dependence of the Brillouin frequency shift on temperature.

This paper discusses the effect of Fresnel reflection on BOTDR measurement. We show that a detectable sensor length can be determined from the intensity of the returning light and it depends on the laser linewidth.