Nec Corporation

Arihide Noda

Jun Sakai

Hideyuki Ono

Hikaru Kouta

Mikio Oda

Takashi Ohtsuka

Hisaya Takahashi

Minoru Shikada

Tomotaka Ishida

Provided is an optical interconnection device in which a volume required for cooling is reduced. In the optical interconnection device, a plurality of optical modules () are arranged on a periphery of an LSI () electrically connected to an electric wiring board (), and liquid cooling mechanisms () are respectively placed on the LSI () and the optical modules (). The plurality of optical modules () may be arranged only on a surface of the electric wiring board () where the LSI () is mounted, only on a surface opposite to the surface where the LSI () is mounted, or on both the same surface as and the opposite surface to the surface where the LSI () is mounted.

Optical interconnection device

An optical modulation device comprises an optical modulator in which the operating point is varied according to a bias voltage. A phase deviation of an operating point from a selected optimal operating point is detected by a phase comparator based on an output light of the optical modulator. The bias voltage is generated within a predetermined voltage range by a DC amplifier so as to reduce the phase deviation. A reset circuit resets the bias voltage at the ground voltage associated with the selected optimal operating point when the optical modulator is powered up and passes the bias voltage to the optical modulator at all other times.

Optical modulation device having bias reset means

A light outputted from a laser diode is intensity-modulated by an optical modulator in accordance with a modulation signal in which a sine wave signal outputted from a low frequency oscillator is superposed on a data signal by a drive amplifier. The output light from the optical modulator is branched by an optical coupler and converted into an electric signal by a light receiving element. A frequency component of the electric signal corresponding to the sine wave signal is extracted by a band pass filter. The extracted electric signal is amplified by a variable gain amplifier with a gain. A phase difference between the amplified electric signal and the sine wave signal is determined by a phase detector and a bias voltage controlled based on the phase difference is supplied from a DC amplifier to the optical modulator. The gain of the variable gain amplifier is changed such that the peak value of the extracted electric signal falls within an allowable voltage range of the phase detector. The operation point can be kept at a stable point even if displacement of the operation point is caused due to temperature change and degradation as time.

Setting operation point in optical modulation apparatus

In a light transmission device operable in response to a sequence of input digital signals to produce an output light beam, a modulated light beam is produced from a laser device as a result of frequency shift keying carried out under a designed modulation index and is transmitted as the output light beam on one hand and is sent to a Fabry-Perot interferometer on the other hand to produce an optical output beam which has an output level deviated in dependence upon a variation of a modulation index relative to the designed modulation index. A feedback signal is fed back to a drive circuit which is supplied with the input signals and which is operable to control the laser device. The feedback signal serves to adjust the modulation index of the laser device to the designed modulation index. A controller may be included to control a central frequency of the output light beam by producing a bias signal which is added to the feedback signal.

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Tokyo, Japan

Arihide Noda