Noriyuki Araki

Maintenance method using 1650-nm wavelength band for optical fiber cable networks

This paper proposes a maintenance method for optical fiber cable networks that uses 1650-nm wavelength band light. We determined the maintenance wavelength of 1650-nm after considering the maintenance system requirements and the future trends in optical transmission systems. We improved the conventional maintenance system by adding appropriate system components including a narrow wavelength light source and a fiber-grating filter for the 1650-nm wavelength band. We designed the system and undertook manufacturing trials. The characteristics of our proposed maintenance method indicate good practical performance levels.

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.

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.

Newly developed optical fiber line testing system employing bi-directional OTDRs for PON and in-service line testing criteria

A passive optical network (PON) that provides fiber to the home (FTTH) services is a fundamental access network topology in Japan. An optical fiber line monitoring and testing system is essential if we are to improve service reliability and reduce the maintenance costs of optical access networks. PONs have optical splitters in their optical fiber lines. It is difficult to find a fault in an optical fiber line equipped with an optical splitter by using a conventional optical fiber line testing system, which uses optical time-domain reflectometer (OTDR) in a central office (CO), because Rayleigh backscattering from the branched fibers accumulates in the OTDR trace. This paper describes a newly developed optical fiber line testing method that employs bi-directional OTDRs with two wavelengths at branched fiber regions in a PON to locate a fault precisely. Optical fiber line testing is conducted by two OTDRs that are installed in a CO and on a customers premises, respectively. The OTDR in the CO has a U-band maintenance wavelength. We present two kinds of maintenance wavelength allocation for OTDRs on a customers premises, which are in the U-band and C-band respectively. An OTDR whose maintenance wavelength is in the U-band enables us to test in-service PON lines simply by filtering the U-band wavelength. For the maintenance wavelengths in the C-band, we can use a cost-effective conventional OTDR to test the PON from the customers premises on condition that we clarify the peak pulse power limit and dynamic range. We describe the test procedures for both cases. We also clarify the insertion loss design for an optical filter in the CO when using the U-band to provide the maintenance wavelength and the criteria for in-service line testing when the using C-band to provide the maintenance wavelength. To confirm the feasibility of our approach, we demonstrate a bi-directional OTDR method using the U-band and the C-band, and the test procedure, which successfully detected fault locations in branched fiber regions. We also describe the use of packet loss measurements to investigate the effect of in-service line testing with an OTDR in the C-band on data communication quality.

Field Trials of PNC-OFDR in Different Environments for Detecting Short Beat Lengths

A spatial resolution of 10 cm was obtained for distances of 60~80 km in different field environments using phase-noise-compensated optical frequency domain reflectometry. The outstanding spatial resolution makes it possible to identify high-birefringence sections along installed cables. In field trials, we successfully observed beat lengths as small as ~20 cm, which showed that there were very large birefringence sections in the installed cables. To the best of our knowledge, this is the first time that such short beat lengths have been directly detected in a nondestructive measurement for long fibers, and the result will be very useful in relation to fiber management.

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.

A New Optical Fiber Line Testing Function for Service Construction Work That Checks for Optical Filters Below an Optical Splitter in a PON

In this paper, we propose a new function for construction work undertaken to install optical fiber lines for services in a passive optical network (PON). This paper describes a novel measurement technique designed to check for optical filters located in front of an optical network unit in branched optical fiber regions in PONs with outside optical splitters. The purpose is to determine whether an optical fiber is ldquoliverdquo or ldquounused.rdquo The features of our proposed technique are the use of test lights operating at two different wavelengths and a nondestructive macrobending technique. By comparing the difference between the reflected powers of the two wavelengths, we can determine the presence of a filter at the end of a fiber line. Furthermore, we describe an enhanced estimation analysis method that uses two photodetectors installed symmetrically in the detection part and an analysis procedure for detecting only a test light reflected from the fiber end. We also demonstrate the performance of the enhanced analysis method experimentally and confirm that it can be employed to detect an optical filter installed at the end of an optical fiber line.

Improvement of fault identification performance using neural networks in passive double star optical networks

Summary form only given. Passive double star (PDS) optical networks are expected to be used to construct low cost access networks for broadband services. We have already proposed a testing method with a dichroic reflective optical (DRO) filter for PDS networks, which identifies faults between an optical line and transmission equipment on the subscriber side. When the reflections are completely separated, we can identify faults with the conventional method described above. However, when the reflections from the filters are superimposed, this becomes difficult and the identification resolution is greatly degraded. This paper proposes a novel software method using neural networks (NN) to overcome this problem.

New optical fiber line testing system function for highly accurate facility location using Brillouin frequency shift assigned optical fiber

This paper describes a new optical fiber line testing system function for locating faulty facilities in optical fiber networks with a high accuracy by using 1 cm of Brillouin frequency shift assigned fiber.