Kazuo Hogari

Measurement of Raman gain distribution in optical fibers

This letter proposes a new technique for measuring the Raman gain characteristics of optical fibers. This method can be used to measure the longitudinal distribution of the Raman gain efficiency of single-mode optical fibers. We demonstrated that the Raman gain efficiency distribution could be measured easily and accurately.

Statistical dispersion budgeting method for single-mode fiber transmission systems

A statistical dispersion budgeting method for spliced single-mode fiber transmission spans is proposed. The method aids in the design of fiber spans in high bit-rate (>1 Gb/s) systems. Intended for spans containing many splices, the method yields, in theory, greater span lengths than those calculated with the traditional worst-case dispersion budgeting method. >

Raman gain efficiency distribution measurement in single-mode optical fibers by using backscattering technique

This letter proposes a new method for measuring a longitudinal distribution of the Raman gain efficiency in concatenations of single-mode optical fibers by using a backscattering technique and a pulsed pump light. The advantages of this method is that it can provide us with an easy operation for measuring optical fiber networks because all the measurement instruments are installed together at one end of the concatenation of optical fibers, and that it also provides a high resolution of the measurement according to the pump pulsewidth. We perform an experiment employing this method and confirm that it can be used to measure Raman gain efficiency distribution easily.

Coated optical fibers for high-strength fusion splices

Suitable fiber-coated structures and a practical splice technique which are superior in both long-term reliability and splice operation efficiency in the field are required. A splice technique without using any dangerous chemical acids to remove the primary coat and coated fiber structures are proposed in this paper. With these techniques, an average strength of 0.88 GPa for bare fusion spliced fibers is obtained in the field, which is more than double the value compared with the average strength of 0.4 GPa obtained by the conventional splicing technique, which is used practically in the field. In addition, the splice time decreases to about one-third of the conventional splice time. The splice operation efficiency improvement is recognized for not only coated mono-fibers but for fiber ribbons.

Technique for measuring longitudinal distribution of Raman gain characteristics in optical fibers

This paper proposes a novel technique for measuring the longitudinal distribution of the Raman gain characteristics in concatenated single-mode optical fibers. This technique has an attractive advantage in that the Raman gain efficiency in concatenated optical fibers can be evaluated individually. We describe a measurement principle for obtaining the Raman gain efficiency distribution in optical fibers. We carried out laboratory and field measurements based on this principle, and confirmed that the Raman gain efficiency distribution could be measured easily and accurately.

Resin selection and high-speed coating of optical fibers with UV-curable materials

As a result of the curing properties of UV-curable resins, a selection criterion for UV-curable resins for high-speed fiber coating is proposed. The method is based on specifying two parameters of a UV-curable resin, which designate the Yongs modulus of cured resin. The method was used to coat graded-index fibers with the selected resins and it was demonstrated that the optical loss changes due to the coating process are small. The change of the fiber ribbon was within 0.1 dB/km under temperature changes between -40 degrees C and +60 degrees C. >

Performance prospects for distributed measurement of Raman gain characteristics in optical fibers

A new technique has already been proposed by the authors for measuring Raman gain characteristics in single-mode optical fibers. The advantage of this technique is that it enables the evaluation of the longitudinal distribution of the Raman gain efficiency in concatenated fibers. With such distributed measurements, it is important to investigate the measurable length, which is determined by the signal-to-noise ratio (SNR) of the detected signal. In this paper, the maximum measurable length available with the previous technique was clarified based on both theoretical and experimental investigation. The SNR of the detected signal has been calculated theoretically, and it has been found that calculated and experimental results were in good agreement. Based on the SNR calculation, the measurable lengths available with this technique for various spatial resolutions and signal wavelengths are discussed.

Distribution measurement of Raman-gain and optical-loss characteristics in optical fibers.

We propose a test method with which to measure the longitudinal distribution of Raman-gain characteristics in connected optical fibers. We describe a technique for obtaining the pump-loss distribution, knowledge of which is necessary for deriving the Raman-gain efficiency distribution, by the bidirectional measurement of Raman amplification. Based on this technique, we performed experiments and demonstrated that the Raman-gain efficiency distribution can be evaluated with the same equipment.

Design and performance of 2000-fiber cable

This paper proposes high-density and high-fiber-count optical fiber cable, containing fiber ribbons inserted into slots and with a total number of fibers exceeding the current maximum of 1000. Cable structure and cable diameter, which are important factors for economical and efficient construction, are investigated theoretically and experimentally and the optimum structure for achieving small cable diameter is obtained. Based on the results, a 2000-fiber cable was manufactured and its performance was evaluated. The transmission, mechanical and midspan access characteristics of the cable was confirmed to be excellent

Design and characteristics of multi-hundred-core optical-fiber cable for use in subscriber feeder lines

This paper describes a design method for optical-fiber cable consisting of optical-fiber ribbons encased in loose tubes. The influence of excess fiber length on optical loss in a loose tube is evaluated and the required clearance is obtained. The optimum combination of the clearance and the tube stranding pitch is obtained in order to suppress fiber strain. The tube dimensions are also discussed and are determined to protect fiber ribbons from lateral load. A 600-fiber-structure cable is manufactured according to the obtained design results; the transmission and mechanical performances are confirmed to be excellent.