JPH01291213A - Fast optical modulator - Google Patents

Abstract

PURPOSE:To reduce the loss of light power and to enable faster modulation by obtaining light pulses which have short pulse width periodically in parallel by a combination of a light emitting means and a branching means or plural light emitting means. CONSTITUTION:The light pulses which has short pulse width of about one psec are obtained periodically in parallel by a mode-lock semiconductor laser 1 and a branch waveguide 2. Those light pulses are modulated independently by an electrooptic modulator array 3 (electrooptic modulators 31-38) and then inputted to a delaying and multiplexing part 4. The input modulated pulses are delayed, bit by bit, at a delay part 4a and further multiplexed at a multiplexing part 4b, so that the modulated pulses are outputted in time series at intervals of about one psec. Consequently, an extremely fast modulating speed is realized, a bistable element is not necessary, and the loss of the light power is suppressed extremely small.

Description

[Detailed Description of the Invention] [Summary] Regarding a high-speed optical modulator capable of high-speed optical modulation, the purpose is to reduce optical power loss and enable high-speed modulation of layers. A light emitting means for periodically generating pulses, a branching means for branching the light pulse outputted from the light emitting means and outputting a plurality of light pulses, and a plurality of light pulses output from the branching means each independently. A modulation means for modulating, a delay means for applying different delays to each of the plurality of optical pulses output from the modulation means, and a synthesis means for synthesizing the optical pulses sequentially output from the delay means into a time-series signal. The system is configured to have the following.

[Industrial application field]

The present invention relates to a high-speed optical modulator capable of high-speed optical modulation.

[Conventional technology]

Conventionally, optical modulators have been ones that directly modulate a semiconductor laser to obtain modulated light, or L i N b
A device in which external modulation is performed by an optical switch using an electro-optic material such as 03 is known.

[The problem that the invention attempts to solve]

” With a conventional dual optical modulator, at most 10 G l
Only a modulation speed of about 1z can be obtained, and it is currently difficult to achieve a higher modulation speed.

In response, the present inventors utilized the parallelism and high-speed limiter characteristics of optical bistable elements, as well as optical pulse delay and synthesis technology, to develop optical modulation that enables high-speed processing beyond 10G IIZ. proposed a container (patent application Sho 61-275゛386
(see issue). However, this optical modulator has the problem that the peak output of the modulated light inevitably becomes small due to the large optical pulse loss caused by the optical bistable element. Since the pulse width is at least several tens of psec, there is also the problem that this limits the modulation speed.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to reduce optical power loss and enable high-speed modulation in the negative order.

[Means to solve the problem]

For example, a light emitting means that periodically generates short light pulses, such as a mode l cock semiconductor laser, is used. and,
A branching means for branching the light pulse outputted from the light emitting means to output a plurality of optical pulses, and a modulation means such as an electro-optic modulator for independently modulating the branched optical pulses are provided. Further, a delay means for applying different delays to the output pulses from the modulation means, and a synthesis means for synthesizing the optical pulses sequentially obtained thereby to form a time-series signal are provided.

Alternatively, a plurality of the light emitting means may be used to eliminate the need for the branching means, and the same modulating means, delay means, and combining means as described above may be provided at the subsequent stage.

Alternatively, in each of the above-mentioned configurations, the arrangement of the modulation means and the delay means may be exchanged with each other.

[Function] ” A plurality of light pulses with short pulse widths can be obtained in parallel and periodically by a combination of the above-mentioned light emitting means and branching means, or by a plurality of light emitting means.For example, a moderonc semiconductor laser can be used as the light emitting means. If the pulse width is approximately 1
Short pulses of 'psec are obtained periodically. next,
Such a plurality of optical pulses are converted into a plurality of modulated pulses whose timings differ from each other by a modulation means and a delay means. Continuing, these modulated pulses are synthesized by the synthesizing means, so that the light emission I'? 7
A time-series signal containing all of the plurality of modulated pulses in one period is obtained. Therefore, in the end, a large modulation rate equal to the 141-digit value of the number of pulses (or the number when a plurality of light emitting means are used) obtained by branching the light emitting means by the branching means is obtained in the light emitting frequency of the light emitting means.

Moreover, since a light emitting means capable of outputting short pulses is used, a conventional optical bistable element is no longer necessary, and it is therefore possible to extremely reduce the loss of optical power.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the high-speed luminous intensity 8-point device of the present invention.

In the figure, one Morlock semiconductor laser 1 is provided as a light emitting means. Although this mode-locked semiconductor laser 1 cannot be modulated by itself, it can periodically emit short optical pulses with a pulse width of about 1 psec (for example, 10 G Ilz) with a peak output of about 5 W. can.

Furthermore, a plurality of optical pulses (81 [1i1 in the figure)
It is equipped with a branching waveguide 2 that branches into parallel optical pulses, and on its output side there are eight electro-optic modulators (for example, LiNb) that independently modulate the branched optical pulses.
An electro-optic modulator array 3 consisting of O3 modulators 31-38 is provided.

Further, at the subsequent stage of the electro-optic modulator array 3, there is a delay and synthesis unit 4 which applies different delays to the eight optical pulses outputted in parallel from the electro-optic modulator array 3 and synthesizes them into a time-series signal. LJ has been established. A specific example of this delay and synthesis unit 4 is shown in FIG.
+, eight waveguides 41 with slightly different lengths
48, and a combining section 4b where these waveguides merge into one waveguide 40. In FIG. 4(b), there is a delay section 4a' consisting of eight optical fibers 41' to 48' with slightly different lengths,
It consists of a combining section 4b' where these optical fibers merge into one optical fiber 40'. Here, if the lengths of the waveguides 41 to 48 or the optical fibers 41' to 48' are set to have a difference of about 1 inch, a corresponding delay of about 10 psec can be generated. can. In addition, in the same figure (C1, other waveguides 41'' to 41'' with different refractive indexes and slightly different lengths are provided in the middle of the eight waveguides on the input side that have the same length. 48
and a combining section 4b'' in which the input waveguide merges into one output waveguide 40''. Even with such a configuration, each input pulse is delayed depending on the length of each of the waveguides 41'' to 48''. Alternatively, the waveguides 41'' to 48'' may have the same size and have slightly different refractive indices.

In the high-speed optical modulator of this embodiment, which has the following two configurations, first, a mode-locked semiconductor laser 1 and a branching waveguide 2 are used to generate a plurality of b optical pulses with a pulse width as short as 11) SeC. obtained in parallel and periodically. Subsequently, such a plurality of optical pulses are each independently modulated by the electro-optic modulator array 3 (electro-optic modulators 31 to 38), and then input to the delay and combination unit 4. Then, the plurality of input modulated pulses are transmitted to the delay section 4a (shown in FIG. 2).
4a'.

4, a''), and are further synthesized by the synthesizing section 4b (4b', 4b''), so that the above-mentioned modulated pulses are outputted in time series at approximately 1 psec intervals. That is, a time-series signal including all of the plurality of modulation pulses within the emission period of the mode-locked semiconductor laser 1 is obtained.

Therefore, the emission frequency of the motor semiconductor laser 1 is set to 1.
0 G llz and the number of electro-optic modulators is N (N-8 in Figure 1), etc.
A modulation rate of llz is obtained. In Figure 1, N=
8, but it is also possible to configure the electro-optic modulator array 3 so that, for example, N = '1Ot), so in this case, 100 x 10Gllz = I Tl
An extremely large modulation speed of 1z is achieved. Moreover, in this embodiment, since the mode-locked semiconductor laser 1 that can periodically output short pulses of about 1 psec is used as described above, an optical bistable element like the conventional one is not required, and therefore the optical power loss can be kept extremely small.

Next, another embodiment of the present invention is shown in FIG.

In the figure, a mode-locked semiconductor laser 11 to 19 is arranged in parallel, instead of one mode-locked semiconductor laser 1 and branch waveguide 2 in FIG. 1. A lock semiconductor laser array 10 is used. With this configuration, the output light from each of the mode-locked semiconductor lasers 11 to 19 is not split, so that a much stronger output light intensity can be obtained than in the embodiment shown in FIG.

In each of the embodiments shown in FIGS. 1 and 3 above, the electro-optic modulator array 3 is connected to the delay section 4a (4a', 4a'') and the synthesis section 4b (4b', 4b',
4b''), similar effects can be obtained.

Further, instead of the mode-locked semiconductor lasers 1 and 11 to 19, other light emitting means that can periodically generate light pulses shorter than a normal semiconductor laser may be used.

[Effects of the Invention] As explained above, according to the high-speed optical modulator of the present invention,
Modulation speed can be significantly improved, and optical power loss can be minimized to obtain a large peak output.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, FIG. 2 (al to tc+ is a block diagram showing a specific example of the delay and synthesis section 4, and FIG. 3 is a block diagram of another embodiment of the present invention. 1...Mode-locked semiconductor laser, 2...Branch waveguide, 3...Electro-optic modulator array, 31-38...Electro-optic modulator, 4...Delay and synthesis section, 4a , 4a', 4a#... Delay section, 4b, 4b', 4b#... Composite diagram. 10... Mode-locked semiconductor laser array, 11-1
9...Modoro-7ri semiconductor laser. Patent applicant Fujitsu Ltd. Nozuya's Kumusegri Figure 3

Claims (1)

[Scope of Claims] 1) A light emitting means (1) that periodically generates short light pulses; and a branching means (2) that branches the light pulse output from the light emitting means to output a plurality of light pulses. , a modulation means (3) for independently modulating the plurality of optical pulses outputted from the branching means; and a delaying means (4a) for applying different delays to the plurality of optical pulses outputted from the modulation means. A high-speed optical modulator characterized in that it comprises a synthesizing means (4b) which synthesizes the optical pulses sequentially outputted from the delay means to form a time-series signal. 2) A plurality of light emitting means that periodically generate short light pulses (
10), modulation means (3) for independently modulating the light pulses output from the plurality of light emitting means, and delay means (4a) for applying different delays to the plurality of light pulses output from the modulation means. ), and a synthesizing means (4b) that synthesizes the optical pulses sequentially output from the delay means to form a time-series signal. 3) A light emitting means (1) that periodically generates short light pulses, a branching means (2) that branches the light pulse output from the light emitting means and outputs a plurality of light pulses, and an output from the branching means. a delay means (4a) that applies different delays to the plurality of optical pulses output from the delay means; a modulation means (3) that independently modulates the optical pulses sequentially output from the delay means; A high-speed optical modulator comprising: a combining means (4b) that combines optical pulses into a time-series signal. 4) A plurality of light emitting means that periodically generate short light pulses (
10); delay means (4a) for applying different delays to the light pulses output from the plurality of light emitting means; and modulation means (3) for independently modulating the light pulses output from the delay means; A high-speed optical modulator comprising: a combining means (4b) that combines optical pulses sequentially output from the modulating means to form a time-series signal.