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Title:
DIFFERENTIAL FOUR-PHASE SHIFT MODULATOR AND METHOD FOR CONTROLLING PHASE SHIFT AMOUNT THEREOF
Document Type and Number:
WIPO Patent Application WO/2007/116475
Kind Code:
A1
Abstract:
A differential four-phase shift modulator wherein a low-cost photoelectric conversion element, the response rate of which is sufficiently lower than the bit rate, is used to achieve a feedback control of a phase shift amount such that two multiplexed differential phase shift modulated optical components, which exhibit differential four-phase shift modulated light, have appropriate phase difference therebetween. For this purpose, the inventive apparatus is composed such that drive signals, which have different duty ratios, are applied to a first modulator (2-1) and a second modulator (2-2), whereby the average optical output power of a differential four-phase shift modulated light outputted by a multiplexing part (16b) can vary in accordance with the phase difference between the first and second optical signal components as multiplexed by the multiplexing part (16b). The inventive apparatus comprises a power monitor (18) that monitors the average optical output power of the differential four-phase shift modulated light; and a phase shift control part (19) that performs, based on the average optical output power monitored by the power monitor (18), a feedback control of the phase shift amount in a phase shifting part (14).

Inventors:
TERAHARA TAKAFUMI (JP)
HOSHIDA TAKESHI (JP)
NAKAMURA KENTARO (JP)
AKIYAMA YUICHI (JP)
OOI HIROKI (JP)
JENS C RASMUSSEN (JP)
MIURA AKIRA (JP)
Application Number:
PCT/JP2006/306870
Publication Date:
October 18, 2007
Filing Date:
March 31, 2006
Export Citation:
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Assignee:
FUJITSU LTD (JP)
TERAHARA TAKAFUMI (JP)
HOSHIDA TAKESHI (JP)
NAKAMURA KENTARO (JP)
AKIYAMA YUICHI (JP)
OOI HIROKI (JP)
JENS C RASMUSSEN (JP)
MIURA AKIRA (JP)
International Classes:
G02F1/03; H04B10/50; H04B10/556
Domestic Patent References:
WO2003049333A12003-06-12
WO2004088397A12004-10-14
Other References:
See also references of EP 2003486A4
Attorney, Agent or Firm:
SANADA, Tamotsu (10-31 Kichijoji-honcho 1-chome,Musashino-sh, Tokyo 04, JP)
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