Acoustic time-domain reflectometer used as a short-range fiber-optic fault locator

Difficulties arise in detecting a fault in an optical fiber, when an optical time-domain reflectometer is used for fiber with a tilted surface fracture. The difficulty arises from the fact that the optical reflection coefficient becomes too small to be detected. As an alternate means, an acoustic time-domain reflectometer was attempted. Some experimental results are presented.     

Millimeter-resolution optical time-domain reflectometry using afour-wave mixing sampling gate

We report an optical time-domain reflectometer that employs an ultrafast optical switch based on nondegenerate four-wave mixing in a semiconductor laser amplifier. Two-point spatial resolution on the order of 1 mm over 2 m is demonstrated; Fresnel reflections with optical return losses greater than 53 dB are detected. Submillimeter-resolution optical time-domain reflectometry over a 100-m range should be possible with modifications to the pulse sources     

Optical time-domain reflectometer with a semiconductor laser amplifier

An optical time-domain reflectometer (OTDR) using a semiconductor laser as an optical pulse generator and as a back-scattered optical signal amplifier is reported. It is found that the detectable one-way loss of the apparatus is improved by 4.5 dB compared with the conventional OTDR using direct detection.     

New simple one-end splice loss measurement method using an OTDR for single-mode optical fibre

The letter presents a new simple method using an optical time-domain reflectometer for measuring the real splice loss of single-mode optical fibres from one end of the fibre. Importantly, the method eliminates the difference in backscattering properties of the spliced fibres by subtracting two discontinuities obtained at different wavelengths in the received backscattered power.     

OTDR in single-mode fibre at 1.5 ?m using heterodyne detection

Heterodyne detection has led to a significant improvement in the range performance of an optical time-domain reflectometer designed to operate on single-mode fibre at a wavelength of 1.52 ?m. With only 5 ?W peak launched power a range of 30 km was achieved.     

Real-time long range complementary correlation optical time domainreflectometer

The improved performance of an optical time-domain reflectometer (OTDR) through the application of a correlation technique using codes with complementary autocorrelation properties is discussed. The theoretical foundations of the method are presented along with experimental results exhibiting the best one-way range reported to date for a practical long-haul, long-wavelength OTDR system     

Photon-counting optical time-domain reflectometer using a planar InGaAsP avalanche detector

We demonstrate the first room-temperature photon-counting optical time-domain reflectometer, which uses a planar InGaAsP avalanche photodiode. Using a 1.3 ?m semiconductor laser source we achieve a one-way loss sensitivity of 20 dB.     

Novel OTDR Technique for Measuring Relative-Index Differences of Fiber Links

A novel technique is proposed for measuring the relative-index difference of the fiber links using an optical time-domain reflectometer (OTDR). The material dispersion of the fiber links can be estimated by using this method. Moreover, the chromatic dispersion distribution of a fiber link is successfully estimated by combining this technique with the conventional OTDR technique     

Measurement of the spatial distribution of birefringence in opticalfibers

We describe a technique for the measurement of the birefringence spatial distribution in a single-mode optical fiber with a resolution of 1 m. This technique is based on a polarization optical time-domain reflectometer using a rotary linear polarizer. We report results performed on different types of fibers: standard step-index and dispersion shifted fibers     

Ultra-long-range OTDR in single-mode fibres at 1.3 ?m

A single-mode optical time-domain reflectometer (OTDR) operating at a wavelength of 1.3 ?m with a dynamic range in excess of 26 dB one way is reported. The equipment incorporates a semiconductor laser source and a new low-noise optical receiver design utilising a PIN diode detector and a transimpedance amplifier.     

Design of a 1.65-μm-band optical time-domain reflectometer

The design and performance of a 1.65-μm-band single-mode optical time-domain reflectometer (OTDR) with a laser diode source are described. The approach employs a high-power laser diode with a strained-layer InGaAs/InGaAsP multiple-quantum-well (MQW) structure which is grown by metalorganic vapor phase epitaxy (MOVPE), an InGaAs avalanche photodiode, and methods for reducing the optical wiring loss in an optical unit. A 1.65-μm-band OTDR is realized with a single-way dynamic range of 25 dB at a pulse width of 1.0 μs     

Design and performance of a novel automatic fiber line testingsystem with OTDR for optical subscriber loops

This paper proposes architecture for a novel automatic fiber line testing system with an optical time-domain reflectometer (OTDR) and describes the system requirements, the design method, and the system evaluation. The results of a trial on a manufactured system and an evaluation of its characteristics are presented with evidence that an in-service optical fiber can be tested with no degradation in communication quality and the desired measurement accuracy and system component characteristics can be realized. In addition, it is confirmed that a failure between an optical fiber cable and a digital service unit (DSU) can be identified with 100% accuracy     

Fiber-optic reflection measurements using OCWR and OTDR techniques

A method for determining the backscatter and reflection responses of an optical fiber and reflector to an arbitrary input is developed. Two cases are specifically considered: a continuous-wave input and a rectangular pulse input. From the rectangular pulse input response, the equation is derived for computing the reflectance of a discrete component from an optical time-domain reflectometer (OTDR) measurement. Precautions are given for accurately performing reflectance measurements using an OTDR. Two methods are presented for determining the backscatter level of the fiber type under test, and its importance in reflection measurements is shown     

Long-range OTDR for single-mode optical fibre using a P2O5 highly doped fibre Raman laser

A wide-dynamic-range single-mode optical time-domain reflectometer using a P2O5 highly doped fibre Raman laser and a cooled Ge-PIN photodiode has been realised for the first time. The maximum detectable one-way loss was improved to 35dB in the 1.5 ?m wavelength band.     

Tunable OTDR Based on Direct Modulation of Self-Injection-Locked RSOA for In-Service Monitoring of WDM-PON

We propose a tunable optical time-domain reflectometer (OTDR) for in-service monitoring of wavelength- division- multiplexing passive optical networks (WDM-PONs). The proposed method uses a reflective semiconductor optical amplifier, which is self-injection-locked by a tunable fiber Bragg grating. The proposed tunable OTDR has a tuning range of 30 nm and a resolution of 50 m. The performance of the proposed scheme is experimentally evaluated to demonstrate the in-service monitoring of WDM-PON.     

An optical time-domain reflectometer with low-power InGaAsP diode laser

An optical time-domain reflectometer (OTDR) suited for operation with low-power (of the order of 1-mW peak power) InGaAsP lasers is described. To launch maximum average power into the fiber, the laser is modulated by a pseudonoise binary sequence, and the back-scattered signal is averaged and then analyzed by a microcomputer. Initial tests of the reflectometer with a germanium avalanche photodiode (Ge APD) detector demonstrate backscattering signal levels at 1300 nm from 50-μm core diameter graded-index fibers of more than 15 dB above the system noise.     

Fiber-Optic Distributed Strain and Temperature Sensing With Very High Measurand Resolution Over Long Range Using Coherent OTDR

We describe a novel fiber-optic technique for measuring distributed strain and temperature that uses a coherent optical time-domain reflectometer (OTDR) with a precisely frequency-controlled light source. Using this technique, we achieved temperature measurements in an 8-km-long fiber with a resolution of 0.01degC and a spatial resolution of one meter. This temperature resolution is two orders of magnitude better than that provided by the Brillouin based sensing technique.     

Optical Fiber Cable Measurements in the Field

The optical fiber cable measurement instruments developed by NTF for field use in the 1.3 μm wavelength are discussed. The properties of a stabilized optical light source for single-mode fiber attenuation measurement, optical time-domain reflectometer using a Q-switched Nd:YAG laser as a light source, and chromatic dispersion measurement instrument are described. From the measurement results, these instruments are revealed to be suitable in constructing and maintaining singlemode fiber optical transmission lines.     

Centralized in-service OTDR testing in a CWDM business access network

This paper describes "virtual common space", an access architecture that uses inexpensive "coarse" wavelength-division-multiplexing (CWDM) technology to extend the advantages of wavelength-division multiplexing (WDM) to business access applications. This new approach suggests new operations and diagnostic requirements. A wavelength-selective optical time-domain reflectometer using CWDM sources is demonstrated for such procedures. Some of the potential impairments that could arise from in-service monitoring on these systems are quantified.     

An acoustooptical directional coupler for an optical time-domain reflectometer

An optical directional coupler in which a TeO2acoustooptical deflector (AOD) is employed has been designed and developed for use in an optical time-domain reflectometer (OTDR). A low round-trip insertion loss of 4.6 dB and low crosstalk of below -48 dB were attained for the fabricated coupler. Signals of large amplitude, such as Fresnel reflection, could be suppressed to less than - 33 dB by switching of the optical directional coupler. Amplitude fluctuation of the back-scattered signal due to polarization fluctuation in single-mode fibers is reduced to a negligible extent.