Higher-density single-mode optical fibre cables than 1 fibre/mm2, containing hundreds of fibres

A slotted-rod structure was investigated to obtain the maximum fibre density of high-fibre-count cables. A 500-fibre cable with a fibre density of 1.5 fibres/mm2 was designed and manufactured. The manufactured cable was composed of 10-fibre ribbons inserted into the designed slots. The optical losses of the cabled single-mode fibres were confirmed to be stable at 1.3 and 1.55 ?m. This cable has the highest fibre density of existing optical cables.     

A highly reliable GaInAs-GaInP 0.98-μm window laser

A novel window structure realized by selective N ion implantation and subsequent rapid thermal annealing has been applied to overcome the catastrophic optical damage (COD) of a GaInAs-GaInP laser emitting in the 0.98-μm wavelength region. A kink-free output power up to 220 mW at 25°C was obtained. Laser characteristics including the I-L, far-field pattern, and lasing spectrum were almost the same as those of a conventional nonwindow laser consisting of the same structure except for the window region. In a 50°C, APC-150 mW aging test, the window lasers have operated stably beyond 16 000 h, and no damage has been observed. Under this aging condition, a median lifetime of 280 000 h was obtained from log-normal plotting of aging characteristics. This marked improvement in reliability is due to a remarkable increase of damage tolerance realized by the window structure. In addition, there was minimal change in the characteristic of the window laser during the aging, indicating the absence of serious inner degradation. These results clearly show that our 0.98-μm window laser suppresses both COD failure and inner degradation satisfactorily and can be used in practical applications     

A dispersion compensator using coupled defects in a photoniccrystal

We propose a new type of dispersion compensator that uses the characteristics of light traveling in a coupled defect waveguide (CDW) in a photonic crystal. By using a theoretical computation based on the plane-wave method, we show that the CDW band appears within the bandgap and its characteristics are well reproduced by the tight-binding (TB) model. We calculate the wavelength dispersion of light propagating in the CDW using TB formalism. The calculated result shows an inherently large dispersion of the CDW, which enables the realization of an extremely small dispersion compensator of a few tens of millimeters in size     

Optimum clearance design for a loose optical-fiber cable based on suppression of fiber strain

Theoretical and experimental investigations were made for fiber strain in a loose-type optical-fiber cable. Calculation formulae were derived for strain evaluation, including clearance in a loose-tube. Loose-type optical cables composed of five-fiber ribbons were manufactured and the strain characteristics were measured under tensile force, bending, and temperature change. The theoretical and experimental results were compared and strain reduction was confirmed due to the clearance. By using the results, a design procedure for optimum clearance has been shown, based on strain suppression under an allowable value for long-term use.     

Reduced pressure collapsing MCVD method for single polarization optical fibers

A simple fabrication method of single polarization optical fibers has been proposed. Core, clad, and jacket layers are deposited in a silica tube. The tube is then collapsed while the inner pressure of the tube is reduced. The core circularity and the jacket ellipticity are controlled by the careful selection of the softening points of core/clad and jacket materials, and the inner pressure. The pressure reduction and the softening points of the constituent glasses play an important role in fabricating single polarization optical fibers.     

Elastic basket switching

This paper proposes a new integrated switching system, ‘elastic basket switching’, for broadband and multimedia communications, including voice and high-speed data. In elastic basket switching (EBS), it is possible flexibly and efficiently to handle multimedia information by adaptively assigning communication resources according to communication requests and bandwidth of switched information. For continuous information, such as voice, EBS functions just as a circuit switching system, and for burst data it achieves high-efficiency bandwidth usage equivalent to a packet switching system by demand-assign type time-slot assignment. The detail of EBS and its application to a departmental system-orientated PBX are described. The traffic handling capability and details of the hardware structure are presented. The experimental system, including use of LSIs in the main parts of EBS is also described.     

Suitable parameters of single-mode optical fibre

A new method for determining suitable single-mode fibre parameters is examined. Suitable fibre parameters are determinable by minimising cabling- and splicing-loss increases. An eight-fibre cable was manufactured and the loss increases were measured. ? = 0.2% and V = 2.2 are the values selected using this method and for the experimental results.     

An 8 mm length nonblocking 4×4 optical switch array

A novel single-mode-single-slip-structure S³ optical switch using carrier-induced refractive index change is proposed as a unit cell for a small polarization-independent nonblocking N×N optical switch array. Sixteen S³ optical switches have been integrated into a nonblocking 4×4 optical switch array on an InP substrate. The 8-mm-length InGaAsP/InP 4×4 optical array has shown satisfactory switching characteristics and is suitable for larger scale integration of optical switch arrays and also for integration with other active optical devices such as laser diodes