Abstract: According to one embodiment, a signal transmission circuit includes: a first electro optical converter converting a read electric signal to a first optical signal having an optional wavelength ?R; a first photo-electric converter configured to reconvert the first optical signal to the read electric signal; a second electro optical converter converting a electric signal to be recorded to a second optical signal having a wavelength ?W different from the ?R; a second photo-electric converter reconverting the second optical signal to the electric signal to be recorded; a first optical multiplexer/demultiplexer connected to the first electro optical converter and the second photo-electric converter, and multiplexing and demultiplexing the first and second optical signals; a second optical multiplexer/demultiplexer multiplexing and demultiplexing the first and second optical signals; and an optical transmission medium connected to the first and second optical multiplexers/demultiplexers, and transmits the multiplex

Abstract: According to one embodiment, a filter circuit includes: a first circuit to convert an input voltage into a current using a transfer conductance as a conversion coefficient; a capacitor connected to an output terminal of the first circuit; a second circuit connected to the first circuit and capacitor, and configured to convert an input voltage into a current using a transfer conductance as a conversion coefficient; a setting circuit to adjust the transfer conductance of the first circuit from a first signal and a second signal for gain adjustment and generate a third signal for gain adjustment. The output terminal of the first circuit is connected to an output terminal of the second circuit from which a signal inverted with respect to a signal output from the first circuit is output, the first signal is input to the second circuit, and a frequency band is adjusted by the first signal.

Abstract: According to one embodiment, a frequency characteristic adjusting circuit includes a cutoff range adjusting module and a control signal inputting module. The cutoff range adjusting module is connected to an AC coupling circuit capacitively coupled with a signal transmission path, and allows an output signal from the AC coupling circuit to pass through such that a low cutoff range in the frequency characteristic of the AC coupling circuit varies. The control signal inputting module receives a control signal to control a zero-point frequency based on a numerator polynomial of a transfer function of the cutoff range adjusting module and a pole frequency based on a denominator polynomial of the transfer function. The numerator polynomial is equalized to a denominator polynomial of a transfer function of the AC coupling circuit by the control signal. A cutoff frequency is determined by the pole frequency according to the control signal.

Abstract: An active band-pass filter has a negative feedback circuit including a series-connection of a band-pass block, a second-order band-elimination block having a denominator polynomial equal to the band-pass block and an amplifier block which amplifies the output of the band-elimination block. The band width can be controlled independently of the frequency, adjustment is made easy, and moreover the circuit configuration can be simplified.

Abstract: A thermal-assist magnetic recording device performs a thermal-assist magnetic recording to achieve high density recording compatible with high speed transfer at low cost. The thermal-assist magnetic recording device includes a signal selector circuit that selects a read signal from the read element at the time of reading by the read element, selects a write signal to the write element at the time of writing by the write element and drives the light transmission unit by the selected signal, and an output light selection unit that outputs an output light from the light transmission unit, as either an optical signal at the time of reading or a thermal assist light for applying the heat at the time of writing.

Abstract: A information storage device has a head slider having a flying height control mechanism and a recording and reproducing head, a low frequency superposed circuit that superimposes a low frequency voltage to a flying height adjustment signal to adjust the flying height of the head slider, and a polarity discrimination section that discriminates the polarity of the low frequency detection signal to the low frequency voltage through comparison of the low frequency voltage with the low frequency detection signal. When the polarity of the low frequency detection signal to the low frequency voltage is a negative polarity, the flying height adjustment signal is subtracted by a predetermined value, so that the flying height of the head slider is increased by the correspondence.

Abstract: A determining unit determines whether a clock signal is oscillated with an oscillation amplitude equal to or greater than a predetermined value. An output control unit outputs the clock signal to an output destination when the determining unit determines that the clock signal is oscillated with the oscillation amplitude equal to or greater than the predetermined value.

Abstract: One aspect of the embodiments utilizes a filter circuit which can be connected to a signal source has a low-frequency cutoff of 1/(R×C). The filter includes a buffer circuit which can be connected to an output end of the signal source and has an output impedance of R, and a capacitor which is connected to an output end of the buffer circuit in a floating state and has a capacitance of C/2. The filter includes a resistor circuit which is connected to an output end of the capacitor and has a resistance value of R.

Abstract: A determining unit determines whether a clock signal is oscillated with an oscillation amplitude equal to or greater than a predetermined value. An output control unit outputs the clock signal to an output destination when the determining unit determines that the clock signal is oscillated with the oscillation amplitude equal to or greater than the predetermined value.

Abstract: The present invention is directed to provide a small sized optical apparatus, with low cost and low loss, by realizing a simple structure optimum to bidirectional optical communication. To this end, the present invention comprises three optical multiplexing/demultiplexing sections, in order to make a transmitted light and a received light transmitted bidirectionally in the same transmission path fiber into the light in a single direction, to give these to a single optical processing section (34). The first optical multiplexing/demultiplexing section (31) is connected with a transmission path fiber (2) at a multiplexing side port thereof.

Abstract: The present invention relates to a control method and device for an optical filter, and a primary object of the present invention is to achieve accurate tracking control of the optical filter. Disclosed herein is a control method for an optical filter including first and second optical filter units cascaded, each having an input and first and second outputs. The first output of the first optical filter unit is connected to the input of the second optical filter unit. First light output from the second output of the first optical filter unit is converted into a first electrical signal having a level corresponding to the power of the first light, and second light output from the second output of the second optical filter unit is converted into a second electrical signal having a level corresponding to the power of the second light. A control signal is generated according to the first and second electrical signals. Then, the first and second optical filter units are controlled according to the control signal.

Abstract: The present invention has an object to provide a control method and a control apparatus for a variable wavelength optical filter, which can reliably and stably control drive conditions of the variable wavelength optical filter, independent of the number of wavelengths to be selectively separated in collective.

Abstract: The present invention is directed to provide a small sized optical apparatus, with low cost and low loss, by realizing a simple structure optimum to bidirectional optical communication. To this end, the present invention comprises three optical multiplexing/demultiplexing sections, in order to make a transmitted light and a received light transmitted bidirectionally in the same transmission path fiber into the light in a single direction, to give these to a single optical processing section (34). The first optical multiplexing/demultiplexing section (31) is connected with a transmission path fiber (2) at a multiplexing side port thereof.

Abstract: In the control method for the optical filter according to the present invention, WDM signal light obtained by wavelength division multiplexing a plurality of optical signals having different wavelengths is supplied to an optical filter to obtain output WDM signal light including a part of the plurality of optical signals. The output WDM signal light is converted into an electrical signal per wavelength channel of the output WDM signal light. Then, the optical filter is controlled according to the electrical signal so that the characteristic of the optical filter becomes stable.

Abstract: The present invention has an object to provide a control method and a control apparatus for a variable wavelength optical filter, which can reliably and stably control drive conditions of the variable wavelength optical filter, independent of the number of wavelengths to be selectively separated in collective.

Abstract: The present invention relates to a control method and device for an optical filter, and a primary object of the present invention is to achieve accurate tracking control of the optical filter. Disclosed herein is a control method for an optical filter including first and second optical filter units cascaded, each having an input and first and second outputs. The first output of the first optical filter unit is connected to the input of the second optical filter unit. First light output from the second output of the first optical filter unit is converted into a first electrical signal having a level corresponding to the power of the first light, and second light output from the second output of the second optical filter unit is converted into a second electrical signal having a level corresponding to the power of the second light. A control signal is generated according to the first and second electrical signals. Then, the first and second optical filter units are controlled according to the control signal.

Abstract: In the control method for the optical filter according to the present invention, WDM signal light obtained by wavelength division multiplexing a plurality of optical signals having different wavelengths is supplied to an optical filter to obtain output WDM signal light including a part of the plurality of optical signals. The output WDM signal light is converted into an electrical signal per wavelength channel of the output WDM signal light. Then, the optical filter is controlled according to the electrical signal so that the characteristic of the optical filter becomes stable.

Abstract: In addition to the configuration of a conventional optical XC node, a former-stage regenerator for converting optical signals to electrical signals and regenerating optical signals again is provided at an output stage of a demultiplexer and at the input stage of an optical switch unit. Since the regenerator has a 3R function, the regenerator compensates for the influence of the noise and crosstalk generated during propagation in the transmission line, and improves the S/N ratio of the optical signals. Since the optical signals with S/N ratios improved in this way are inputted to the optical switch unit, it is sufficient only if a latter-stage regenerator compensates for the S/N ratio degradation generated in the optical switch unit, and thereby the error rate characteristic of the optical signals can be improved.

Abstract: Optical cross-connect equipment in which the intensity of a signal light input to optical amplifiers is held constant. Optical cross-connect equipment includes an optical pre-amplifier; a demultiplexer for demultiplexing an input multi-wavelength signal light into wavelength-split lights each having different wavelength; and a routing portion for routing each wavelength-split signal light having different wavelength to a desired output port.

Abstract: In addition to the configuration of a conventional optical XC node, a former-stage regenerator for converting optical signals to electrical signals and regenerating optical signals again is provided at an output stage of a demultiplexer and at the input stage of an optical switch unit. Since the regenerator has a 3R function, the regenerator compensates for the influence of the noise and crosstalk generated during propagation in the transmission line, and improves the S/N ratio of the optical signals. Since the optical signals with S/N ratios improved in this way are inputted to the optical switch unit, it is sufficient only if a latter-stage regenerator compensates for the S/N ratio degradation generated in the optical switch unit, and thereby the error rate characteristic of the optical signals can be improved.