Hitachi, Ltd.

Nippon Telegraph and Telephone Corporation

Hitachi Communication Technologies, Ltd.

Takashi Funada

Ryoji Takeyari

Kazuo Hagimoto

Yukihiko Wakai

Yoshimasa Kusano

Masatoshi Shibasaki

Koji Hata

Hiroshi Kuwaki

Yusuke Honda

Takeshi Kiyose

Kenji Kawamura

Hiromi Murakami

Seiji Asai

Susumu Miyagawa

A unit timing signal synchronized with a high-order transmission frame is used for measuring a difference between the number of data pieces of a client signal mapped to the high-frequency frame and the number of data pieces of the output client signal by integrating the difference therebetween for each unit timing signal. Then stuffing and de-stuffing operations are performed so that a integration result is zero.

Stuffing and destuffing operations when mapping low-order client signals into high-order transmission frames

In an electronic apparatus in which plural substrates are arranged in a perpendicular direction between plural cooling fans in a lower part of a case and plural temperature sensors in an upper part of the case, any temperature variation by 2&#xb0; C. in three seconds detected by any one of the temperature sensors is determined to be abnormal, and thermal energy is caused to be discharged from surfaces of substrates on two sides of a flame by raising air flow rates of fans. Expansion of the flame to other substrates is thereby prevented.

Electronic apparatus

A a first clock extraction device included in the receiving section of the optical regenerator recovers a receiving clock. The receiving clock follows the jitter contained in a receiving optical signal caused by fiber wavelength dispersion. The receiving optical signal is detected in synchrony with the receiving clock. A transmission section includes a transmitter for generating a transmission optical signal changed in phase in such a manner as to suppress the stimulated Brillouin scattering and a second clock extraction device for regenerating the transmission clock not following the jitter. The data of the receiving optical signal is processed at a processing unit, and intensity-modulated on the basis of the data thus processed. The timing of this modulation is synchronized with the transmission clock. The receiving clock is synchronized with the jitter, and therefore no logic error occurs. Since the transmission clock does not follow the jitter, the jitter is prevented from accumulating.

Optical regenerator and an optical transmission system

A variable equalization system is disclosed, in which a plurality of amplification cells having a plurality of filter groups with natural frequencies progressively increased four times are connected in series or in parallel, thereby making possible a variable equalization over a wide range of cable length.

Variable equalization system

Growing community of inventors

Yokosuka, Japan

Takashi Funada