Abstract: An optical interface device determines whether frequency deviation of a clock signal corresponding to an optical signal from a client side is abnormal based on a stuff amount when subjecting a data signal corresponding to an optical signal input from the client side to a stuffing process, inserts an alarm indication signal (AIS) indicating that the frequency deviation is abnormal into a predetermined region of a data signal when the deviation is determined to be abnormal, and outputs an optical signal generated corresponding to the data signal to a WDM line side so as to transfer the AIS to another component disposed downstream therefrom, so that locating a site where an abnormal state occurs is made easier.

Abstract: A transfer apparatus includes a receiver to receive an input signal and to extract a clock signal from the input signal, an input signal interruption detector to detect whether an input signal is input, an oscillator, and a frequency setter to set an oscillation frequency of the oscillator such that a difference between the oscillation frequency of the oscillator and a frequency of a frequency division signal into which a clock signal extracted from the input signal is frequency-divided falls out of a passband width of a filter when the input signal interruption detector detects the input of the input signal.

Abstract: A VOA maximum attenuation control circuit has, in addition to a conventional VOA maximum attenuation control circuit, a first resistor and a second resistor, a transistor which is an emitter follower type PNP transistor, and a capacitor. Since charge of the capacitor is 0 volt at the instant when power of the optical interface unit or each optical interface is shifted from OFF state to ON state, current is supplied to a VOA by the transistor in association with shift to the ON state of the power. As a result, attenuation of the VOA reaches maximum. When the capacitor is gradually charged, base potential of the transistor is finally +5 volts, and current is 0 ampere. Then shifting to maximum attenuation control of the VOA by an operational amplifier is realized.

Abstract: When an XFP is plugged into an optical interface unit by live-line plugging, an external bias voltage higher than an internal bias voltage is kept applied to a CDR incorporated in the optical interface unit until the XFP starts up. This prevents exertion of a negative effect on the CDR.

Abstract: An optical interface device determines whether frequency deviation of a clock signal corresponding to an optical signal from a client side is abnormal based on a stuff amount when subjecting a data signal corresponding to an optical signal input from the client side to a stuffing process, inserts an alarm indication signal (AIS) indicating that the frequency deviation is abnormal into a predetermined region of a data signal when the deviation is determined to be abnormal, and outputs an optical signal generated corresponding to the data signal to a WDM line side so as to transfer the AIS to another component disposed downstream therefrom, so that locating a site where an abnormal state occurs is made easier.

Abstract: An optical transmission apparatus according to the present invention connects a terminal apparatus side in which a transmission line is formed by, for example, SONET/SDH, and a WDM side in which a transmission line is formed by, for example, OTU3. The optical transmission apparatus according to the present invention includes a selector that, when an input signal is interrupted or switched, controls a PLL unit so as to switch and obtain a clock signal of a predetermined frequency oscillated by an OSC, corresponding to a frequency of a clock signal of the input signal before being divided to input into the PLL unit, as a clock signal to generate a PLL reference frequency.

Abstract: A transfer apparatus includes a receiver to receive an input signal and to extract a clock signal from the input signal, an input signal interruption detector to detect whether an input signal is input, an oscillator, and a frequency setter to set an oscillation frequency of the oscillator such that a difference between the oscillation frequency of the oscillator and a frequency of a frequency division signal into which a clock signal extracted from the input signal is frequency-divided falls out of a passband width of a filter when the input signal interruption detector detects the input of the input signal.

Abstract: An optical interface method includes producing a digital wrapper signal by synchronizing a client signal that is inputted via an optical transmission channel with an oscillating frequency of a fixed oscillator; returning the digital wrapper signal back into the client signal; and outputting the client signal obtained from the digital wrapper signal by the returning onto the optical transmission channel. The oscillating frequency of the fixed oscillator is set higher than a frequency of the client signal in the optical transmission channel.

Abstract: A VOA maximum attenuation control circuit has, in addition to a conventional VOA maximum attenuation control circuit, a first resistor and a second resistor, a transistor which is an emitter follower type PNP transistor, and a capacitor. Since charge of the capacitor is 0 volt at the instant when power of the optical interface unit or each optical interface is shifted from OFF state to ON state, current is supplied to a VOA by the transistor in association with shift to the ON state of the power. As a result, attenuation of the VOA reaches maximum. When the capacitor is gradually charged, base potential of the transistor is finally +5 volts, and current is 0 ampere. Then shifting to maximum attenuation control of the VOA by an operational amplifier is realized.

Abstract: When an XFP is plugged into an optical interface unit by live-line plugging, an external bias voltage higher than an internal bias voltage is kept applied to a CDR incorporated in the optical interface unit until the XFP starts up. This prevents exertion of a negative effect on the CDR.

Abstract: A reference-clock selection circuit for a communication interface apparatus in which signals are input via a plurality of channels includes an insertion-stuff-bit-amount monitoring unit that monitors an insertion stuff bit amount to be inserted in the signal; a channel detecting unit that detects a channel where the insertion stuff bit amount inserted in the signal matches an insertion stuff bit amount of a reference signal from a reference clock oscillator; and a reference-clock selecting unit that selects the detected channel as a reference clock for network synchronization of a connected network.

Abstract: An optical transmission apparatus according to the present invention connects a terminal apparatus side in which a transmission line is formed by, for example, SONET/SDH, and a WDM side in which a transmission line is formed by, for example, OTU3. The optical transmission apparatus according to the present invention includes a selector that, when an input signal is interrupted or switched, controls a PLL unit so as to switch and obtain a clock signal of a predetermined frequency oscillated by an OSC, corresponding to a frequency of a clock signal of the input signal before being divided to input into the PLL unit, as a clock signal to generate a PLL reference frequency.

Abstract: Optical wavelength converter having a configuration whereby both RZ code and NRZ code can be handled without producing the duty deterioration in the waveform. The optical wavelength converter provided for converting an optical signal in a first optical wavelength band into an optical signal in a second optical wavelength band includes an optical-to-electrical converter for converting an input optical signal into an electric signal; an electrical-to-optical converter for converting the electric signal into an optical signal; and a duty control circuit connected between the optical-to-electrical converter and the electrical-to-optical converter for controlling the duty of the electric signal having been converted by the optical-to-electrical converter according to RZ/NRZ code information.

Abstract: Optical wavelength converter having a configuration whereby both RZ code and NRZ code can be handled without producing the duty deterioration in the waveform. The optical wavelength converter provided for converting an optical signal in a first optical wavelength band into an optical signal in a second optical wavelength includes an optical-to-electrical converter for converting an input optical signal into an electric signal; an electrical-to-optical converter for converting the electric signal into an optical signal; and a duty control circuit connected between the optical-to-electrical converter and the electrical-to-optical converter for controlling the duty of the electric signal having been converted by the optical-to-electrical converter according to RZ/NRZ code information.

Abstract: An optical transmitter includes a laser diode module including a laser diode which outputs a light signal to a transmission line, a driving unit which drives the laser diode in accordance with an input signal indicative of data to be transmitted, and a coupling unit for connecting an output of the driving unit to an input of the laser diode module. The coupling unit allows an alternating current to flow through the laser diode and inhibits the output of the driving unit from being subjected to a direct current from the laser diode module.