Optical modulator

A technology of optical modulators and modulators, applied in optics, instruments, electromagnetic transmitters, etc., can solve the problems that the signal part cannot obtain the waveform shaping effect, and the level of the signal cannot be consistent with the valley of the modulation characteristic, so as to improve the receiving sensitivity , expand the eye aperture, and efficiently transmit information

Inactive Publication Date: 2009-08-05
HITACHI LTD
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Problems solved by technology

However, in binary optical modulation used in general multi-valued optical phase modulation, when the space of a digital signal is transmitted by intensity modulation, since the light intensity cannot be made zero, there is a problem that the level of space and modulation cannot be adjusted. The troughs of the characteristics are consistent, and the waveform shaping effect cannot be obtained in the empty part

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Embodiment 1

[0093] figure 1 As a first embodiment of the present invention, a quaternary optical amplitude modulator 100 is shown.

[0094] The input light 101 provided from the input optical path 102 is branched into a first optical path 104-1, a second optical path 104-2, and a third optical path 104-3 by the optical splitter 103. Among these optical paths, in the second optical path 104-2 and the third optical path 104-3, single-phase MZ-type binary optical phase modulators 105-1 and 105-2 are arranged respectively, and in the first optical path In 104-1 and the third optical path 104-3, optical phase adjusters 106-1 and 106-2 are arranged respectively.

[0095] Separate electrical digital signals are respectively applied to the modulation signal input terminals 112 - 1 , 112 - 2 of the binary optical phase modulators 105 - 1 , 105 - 2 . These telecommunication code rates are the same, and the amount of signal delay is adjusted so that the bit timings coincide with each other. As a...

Embodiment 2

[0120] As a second embodiment of the present invention, Figure 13 A quaternary optical amplitude modulator 100A having an automatic phase adjustment function is shown.

[0121]When the length of each optical path connected to the optical coupler 109 changes, for example, due to a change in ambient temperature or a change over time, the size of the eye aperture of the multivalued light intensity modulation waveform output from the optical coupler 109 changes. , the transmission characteristics deteriorate. When the eye aperture changes greatly, the logic value of the digital signal is inverted, and signal transmission may not be possible. At this time, each phase point also changes in the phase direction, and there is a possibility that transmission deterioration due to waveform chirp may occur, or a large deterioration may also occur in the phase modulation result.

[0122] In the second embodiment, in order to prevent these phenomena, a part of the output light 111 of the ...

Embodiment 3

[0137] As a third embodiment of the present invention, Figure 15 A configuration example of the octal optical amplitude / phase modulator (amplitude binary, phase quaternary) 200 is shown. In this embodiment, the binary optical amplitude modulator 153 which is the basic form of the present invention is used.

[0138] The unmodulated light 151 output from the semiconductor laser light source 150 is input to a well-known quadrature quaternary optical phase modulator (QPSK) 133, and converted into quadrature quaternary phase modulated light 152-1. The quadrature quaternary phase modulated light 152-1 is input to the binary optical amplitude modulator 153, and undergoes chirp-free binary amplitude modulation. Inside the binary optical amplitude modulator 153, the input quadrature optical phase-modulated light 152-1 is branched into a first optical path 104-1 and a second optical path 104-2. The input light of the first optical path 104 - 1 is input into the optical coupler 109 wi...

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Abstract

An optical modulator makes incident light (101) branch off in three optical paths, generates non-modulated signal in the first optical path, generates binary phase modulated light by means of a single phase MZ optical phase modulator in the second and third optical paths, make the non-modulated light and two kinds of the binary modulated light interfere with each other in the same phase at an electric field ratio of 1:a:b to generate 4-valued amplitude modulated light (111) without interference between codes.

Description

technical field [0001] The present invention relates to optical modulators, in particular to multivalued optical modulators suitable for optical information transmission via optical fibers. Background technique [0002] In recent years, the amount of information (transmission capacity) that can be transmitted through a single optical fiber has increased due to the increase in the number of wavelength division multiplexing and the increase in the speed of optical signal modulation. However, it feels like the limit is reached when the transmission capacity reaches about 10T (trillion) bit / s. The reason is that the wavelength band that can be used in optical transmission reaches the limit value determined by the wavelength band of the optical fiber amplifier (combining C, L, and S bands, approximately equivalent to 80nm=10THz), and there is no room for increasing the number of wavelengths. [0003] In order to further expand the transmission capacity of the optical fiber, it i...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G02F1/01H04B10/50H04B10/516H04B10/54H04B10/548
CPCH04B10/541H04B10/548H04B10/505H04B10/5167G02F2001/212G02F1/225G02F1/212
Inventor 菊池信彦
Owner HITACHI LTD
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