Requirements for a telecommunications network are becoming diversified in accordance with progress in social activities. To meet flexibly variable requirements, the telecommunications network should be provided with high capability exchange systems. For such a purpose, the stored program controlled (SPC) switching system may play a key role. In order to process calls in the telecommunications network environment, a signaling system is inevitable. In the telecommunications network, composed of electronic switching systems, the interoffice signaling system should be efficient when handled by a stored program. This paper describes modeling of interoffice signal processing and formulates parameters evaluating signal processing effectiveness. As a numerical example, multifrequency (MF) and common channel (CC) signal processings for a 9 digit transit call in a toll originating switching system served by D-10, N.T.T.'s commercial switching system, are analyzed in an assumed environment of the present analog and the future digital telecommunications network. From the result of this analysis, the paper concludes that a common channel signaling system is effective in the present analog network from the SPC viewpoint. If a digital environment is assumed in the future, a multifrequency-like individual channel signaling system is considered to be effective due to the improvements in dialed number transfer, inherent easy channel state recognition and no necessity for a continuity test. It is also suggested based on the interoffice signal processing analysis to use a common channel signaling system as an interoffice data link between switching offices and a data base, where data on routing (selected speechpath link) or subscriber are stored.

Static characteristics of InGaAsP/InP double-hetero-structure laser diodes with stripe geometry have been examined. Relation between stripe width and "kink power", P_k, where a kink appears in the light output vs. current curve, is demonstrated experimentally. It is shown that a 7 µm-wide stripe laser diode exhibits the stable fundamental transverse mode oscillation as well as the single longitudinal mode oscillation. Growth rate of TM mode is found to be remarkably reduced after TE mode oscillates in the 7 µm-wide stripe mode stabilized laser. The dependence of threshold current, I_th, on the stripe width is examined experimentally and I_th is found to increase when the stripe width is decreased to less than about 10 µm. By taking mode loss into consideration, the increase in I_th with narrowing the stripe width is explained.

This paper proposes a method for calculating transfer function of transmission lines composed of combinations of multimode fibers with arbitrary index profiles. Bandwidths of graded-index fiber transmission lines are estimated taking into account optical equalization, mode conversion and deviation of index profiles from the power-law. Optical equalization greatly improves bandwidths for power-law fibers. As for those which deviate from power-law profile, perturbation of index profiles with low transversal spatial frequency significantly decreases the bandwidth of graded-index fibers. It is important to eliminate the low spatial frequency perturbation in index profiles to provide fibers with wide transmission bandwidths. Bandwidths of transmission lines are estimated when the phase of sinusoidal perturbation in the index profile varies randomly between the fibers at the sending and receiving ends. Calculations suggest that a 100 MHz bandwidth can be expected at a fiber length of 100 km, when deviation from the power-law profile is controlled to within 0.5% of relative index difference between the on-axis and cladding.

This paper considers a two-unit warm standby redundant system. Preventive maintenance (PM) for an active unit is scheduled after a certain period. When an active unit fails or undergoes PM while the other is in standby, the operation is switched to the standby unit. Probability of success in switchover is constant. If the system fails in switchover, the system stops the operation, and resumes it after a certain time. MTTFF, MTBF and steady state availability are obtained. Numerical examples show the effects of PM interval on them.

This correspondence is concerned with finding a set of pels for the prediction of NTSC signal when we are restricted to using a finite number of pels. The forward selection procedure and other methods are discussed, when they are applied to the intrafield prediction of the television signal.

A polarization-independent optical circulator for optical fiber communications is presented. It consists of a YIG Faraday rotator, a quartz half-wave plate and two pairs of rutile prisms. Insertion losses are 2.3 dB and isolations are 33 dB with fiber connection.

The effect of relative refractive index differences of single-mode fibers on zero-dispersion wavelength was investigated. Optimizing the fiber parameters, a single-mode fiber has been realized, which has minimum loss and minimum dispersion at the same wavelength in the 1.5 µm region.