Nazuki Honda

In-Service Line Monitoring System in PONs Using 1650-nm Brillouin OTDR and Fibers With Individually Assigned BFSs

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.

Design of Identification Fibers With Individually Assigned Brillouin Frequency Shifts for Monitoring Passive Optical Networks

We propose a method for monitoring branched sections in passive optical networks (PONs), where identification fibers are used to distinguish each branched section. We clarify the required characteristics for the separation of the Brillouin frequency shifts of each identification fiber. We design and fabricate identification fibers with well-controlled nuB values for PON monitoring based on the required characteristics. The realized Brillouin frequency shift difference is less than 40 MHz from the target, and we achieve a 1-GHz Brillouin frequency shift separation and a 0.06-dB splice loss for standard single-mode fiber. We also demonstrate fault location in a PON using identification fibers connected to a 4-branched splitter. The bending loss in the branched section is successfully located by using the designed identification fibers and a Brillouin optical time domain reflectometer

Extended optical fiber line testing system using new eight-channel L/U-band crossed optical waveguide coupler for L-band WDM transmission

This paper describes the system design for an extended optical fiber line testing system that uses a new L/U-band crossed optical waveguide coupler and a fiber Bragg grating filter for L-band wavelength-division multiplexing transmission. We describe the reflection characteristic required for optical filters located in central offices in order to suppress the ghost signal caused by multireflection in the optical time-domain reflectometry (OTDR) trace. We design and evaluate an eight-channel crossed optical waveguide coupler with a new thin dielectric film filter that separates a 1650-nm test light from the L-band communication light, and confirm that there was no degradation caused by multireflections in the OTDR trace. We also demonstrate the in-service line monitoring of a 10-Gb/s L-band transmission with no degradation in the transmission quality.

Bending and connection loss measurement of PON branching fibers with individually assigned Brillouin frequency shifts

This paper describes the bending and connection loss measurement of PON branching fibers with individual Brillouin frequency shifts and the measurement of the peak spectrum of the Brillouin frequency shifts distributed in test fibers

Spectral filtering criteria for U-band test light for in-service line monitoring in optical fiber networks

In the fiber-to-the-home era, thousands of optical fibers will have to be accommodated in the central offices of optical access networks. To reduce maintenance costs and improve the service reliability of optical fiber networks, the authors must develop an optical fiber line testing system with a function for in-service line monitoring that uses a test light with a wavelength different from the communication light wavelength. To monitor an in-service line in an optical network, the effective rejection ratio of the test light must be taken into account. This ratio depends on the spectrum of the test light from the optical time-domain reflectometer and the rejection band of the filter in front of the optical network unit. The dependence of the effective rejection ratio as a function of the sideband suppression ratio (SBSR) and of the ratio of the rejection band to the bandwidth of the sideband noise d/D is clarified. When d/D=0.1 and the target effective rejection ratio of the filter is -40 dB, the SBSR and the filter loss of the termination cable must be -70 and -43 dB, respectively, or the SBSR must be -80 dB. When d/D<0.5 and the target effective rejection ratio of the filter is -40 dB, the SBSR is also required to be -80 dB. In-service line monitoring for a 10-Gb/s transmission using a 1650-nm test light with an SBSR of -80 dB is also demonstrated.

Individual fiber line testing technique for PON using wavelength assigned FBG termination and TLS-OTDR enhanced with reflected trace analysis method

We describe a fiber line testing technique for PON that uses backscattered light reflected on FBGs with several wavelengths and a TLS-OTDR. We demonstrate the ability to test 8-branched fibers individually.

Facility database-free maintenance system for optical fibre network combined with PON OAM function

We propose and demonstrate a new optical fibre line monitoring system that locates a fault accurately without a facility database. This system operates in combination with the PON OAM function based on an automatically generated round-trip-time in a ranging process.

Individual fiber line testing technique for PONs using TLS-OTDR enhanced with reflected backward light analysis method

We describe a fiber line testing technique for PON that uses backscattered light reflected at FBGs with several wavelengths and a TLS-OTDR. We demonstrate the ability to test 8-branched fibers individually.

Optical Cable Changeover Tool With Light Injection and Detection Technology

We propose a switching equipment that employs a bent fiber and its application for changing optical cables in an access network. This equipment reduces the length of the interruption in the transmission between an optical line terminal and an optical network unit during construction work. We designed the equipment with communication light injection and detection technology.

Fiber Identification Below an Optical Splitter With a Test Light Injection Tool

We propose a novel test light injection tool for fiber identification below an optical splitter in a passive optical network. This tool makes it easy to input a test light into a bent fiber with a lateral light injection technique. We designed a high precision alignment technique to improve the test light injection efficiency and confirmed that the proposed tool can be used for fiber identification below an optical splitter.