Nec Corporation

Masashi Tachigori

Takashi Kuriyama

Yoshihiro Matsumoto

Yoshinori Honma

Tsutomu Tajima

Toshibumi Kawano

Masaki Shiraiwa

Munetoshi Yoshizawa

Hirokazu Kobayashi

Kenzou Tan

A circuit for driving a light-emitting element such as a laser diode LD has a boost circuit for boosting an input voltage to supply it to the light-emitting element, a photoreceptor such as a photodiode PD for monitoring light from the light-emitting element; and a boost control circuit for controlling a boost voltage of the boost circuit based on a monitored amount of the photoreceptor. In the method for driving a light-emitting element by boosting an input voltage to supply the voltage to the light-emitting element, light from the light-emitting element is monitored and its monitored amount is used as a basis to control a boost voltage to the light-emitting element. A control circuit may be provided to control a driving current that passes through the light-emitting element based on the monitored amount of the photoreceptor.

Circuit and method for driving light-emitting element and optical transmitter

A photo receiver branches a data signal obtained by photoelectric conversion and supplies the signal to a signal cutoff detector. Depending on the degree of an autocorrelation of a data signal obtained by an autocorrelation detector, the signal cutoff detector detects abnormality/normality. Depending on a level of a control signal to a VCO contained in a frequency phase-locked loop for use in clock generation, an out-of-synchronization detector makes determination of abnormality/normality. Outputs of both the detectors are ORed at an alarm processor and when at least one of the detectors detects abnormality, the detector generates an alarm.

Signal input cutoff detector, photo receiver and signal input cutoff detecting method

An ECL terminating circuit, in which it is prevented that the amplitude of an output signal from an ECL outputting circuit or a PECL outputting circuit is lowered caused by that the supply voltage for the circuit has been lowered, and also it is prevented that the waveform of the output signal is deteriorated caused by that the distance of a transmission line where the output signal being high speed is transmitted is made to be long, is provided. The ECL terminating circuit consists of a PECL outputting circuit, a resistor, a transmission line, a load circuit, and a terminal element. And the terminal element is connected to the resistor in series and the resistance value of the terminal element is about 0 &OHgr; at a direct current (DC), but is made to be large at an alternating current (AC).

ECL terminating circuit

The present invention provides an automatic identification level control circuit, an identification level control method, an automatic identification phase control circuit, an identification phase control method, and an optical receiver, capable of stably setting an optimal identification level or identification phase. An automatic identification level control circuit of the present invention includes a coupling capacitor, an identification circuit, a level fluctuation detection circuit, an identification voltage control circuit, and a low-pass filter. The identification circuit includes limiter amplifiers and flip flops. The level fluctuation detection circuit includes exclusive OR circuits.

AUTOMATIC IDENTIFICATION LEVEL CONTROL CIRCUIT, IDENTIFICATION LEVEL CONTROL METHOD, AUTOMATIC IDENTIFICATION PHASE CONTROL CIRCUIT, IDENTIFICATION PHASE CONTROL METHOD, OPTICAL RECEIVER, AND OPTICAL COMMUNICATION SYSTEM

On a module substrate on which a wiring pattern is formed, an integrated circuit device is mounted via solder bumps so that the front surface thereof faces the module substrate. An optical fiber is seated within a groove formed on the rear surface of the integrated circuit device. Additionally, a photo-detecting device is mounted on the module substrate for receiving light transmitted through the optical fiber. This allows the photo-detecting module to reduce the number of mounted parts and to be fabricated in less time.

Photo-detecting module having a fiber optic groove on rear surface of integrated circuit device

A preamplifier is provided with a current feedback circuit including an amplifier for amplifying an input optical current and a feedback resistor connected between an input and an output of the amplifier, an average detecting circuit for detecting an average output voltage of the current feedback circuit and a current controlling circuit for distributing the input optical current in accordance with the detected average voltage. With this configuration, it is possible to generate an output voltage keeping an amplitude symmetry in a large voltage range.

Preamplifier

A light-receptive module according to the present invention includes a board, a light-receptive element disposed with a light input face thereof facing toward the surface of the board, and an optical fiber disposed in a slot formed on the surface of the board and coupled with the light-receptive element. The optical fiber has an end face formed obliquely to the surface of the board so that light is emitted toward a light receive face thereof. The end of the slot has a recession formed in parallel with the surface of the board so that it contacts partially with the end face. The end face is formed at a total internal reflection angle so that light emitted from the optical fiber is subjected to total internal reflection. On the board is formed a slot in which the optical fiber is disposed. The optical fiber is secured to the slot in such a way that the end is thrust into a recession formed in the end of the slot.

Light-receptive module and a method for manufacturing the same

An optical device mounting structure of the present invention has an optical device 3 and a substrate for mounting the optical device 3. The optical device 3 includes a surface 3a facing a mounting surface 1a included in the substrate 1. First electrodes 5 are provided on the surface 1a while second electrodes 7 are provided on the surface 3a and respectively facing the first electrodes 5. First connection members 9 intervene between and connect the first and second electrodes 5 and 7. After marks 31a and marks 31b provided on the surfaces 1a and 3a, respectively, have been brought into register, the first connection members 9 and a second connection member 118 are fused with projections 19 and surface 1a contacting each other. The structure allows the optical device 3 to be accurately mounted to the substrate 1 without any adjustment.

Structure for mounting an optical device

A light receiving module of the present invention includes a semiconductor substrate formed with a guide groove and a mount groove for receiving an optical fiber and a light receiving device, respectively. The mount groove includes a mount surface to which the light receiving device is affixed. The mount surface is contiguous with the output end of the guide groove. The light receiving device is inserted into the accurately formed guide groove and then affixed to the mount surface of the groove. The fiber and light receiving device can therefore be accurately positioned relative to each other. This, coupled with the fact that the optical coupling length is reduced because of the close contact of the fiber and light receiving device, implements adjustment-free mounting and therefore high optical coupling.

Light receiving module

The securing structure for optical device and fiber optics of the present invention comprises a substrate having a through hole through which a fiber optics is inserted, and an optical device secured on the plane of substrate at which the through hole opens. The substrate has a first position pattern provided in relation to the location of a through hole on the plane of substrate at which the through hole opens, while the optical device has a second position pattern provided in relation to the location of a light receiving or emitting section. The fiber optics inserted into the substrate can be coupled optically to the optical device from the positional relationship between the first and second position patterns. According to the present invention, since the location of the through hole into which the fiber optics is inserted is identified by the first position pattern, and the location of the light receiving or emitting section of the optical device is identified by the second position pattern, it is possible to align the fiber optics and the light receiving or emitting section of the optical device by aligning the first and second position patterns.

Structure for securing optical device and fiber optics

Output current of light receiving element Dph is converted into a voltage by a core amplification section, and the voltage output is extracted as an amplification output through an outputting circuit section. The output voltage is fed back to the base of transistor T2 of a differential circuit of the core amplification section, by which it is compared with base reference voltage Vref of transistor T1. When the input current is low, the gain of the core amplification section is dominated by the product of the current flowing through transistor T2 and resistor R4, but when the input current is high, the gain is dominated by the product of current flowing through transistor T1 and resistor R3. Consequently, if resistor R3 is set lower than resistor R4, then when the input current is high, the gain margin indicating a degree of stability of the feedback circuit can be made large, and this stabilizes operation of the front-end amplification circuit.

Growing community of inventors

Tokyo, Japan

Masashi Tachigori