CN1705905A - Optical modulating device - Google Patents

Abstract

An optical modulation apparatus is provided which implements a stable amplifying function by reducing the effect of reflected light rays form end faces of a bidirectional optical amplifier by imposing a numerical limitation on the relationship between the gain of the bidirectional optical amplifier and the loss of the optical modulator, or by inserting a polarization rotation section in a reflection type optical modulator including the bidirectional optical amplifier or in a multi-wavelength collective optical modulation system combining the multiple optical modulators. An optical modulation apparatus is provided which implements a stable amplifying function and cost reduction by reducing the effect of reflected light rays by interposing optical isolators at every alternate SOAs in a transmission-type optical modulation apparatus including a plurality of semiconductor optical amplifiers (SOAs) connected in a multistage fashion.

Description

Optic modulating device

Technical field

The present invention relates to be used for the optic modulating device of optical communication, particularly relate to the formation technology of the optic modulating device that the image intensifer of semiconductor optical amplifier and so on and light intensity modulator is combined and constitute.

Background technology

People were studying always the multi-wavelength light that comprises a plurality of light carriers that produce with light short-pulse laser or amplitude modulation/phase modulation had been used for the mode that wavelength-division multiplex (WDM, Wavelength Division Multiplexing) signal transmits in the past.The spectrum of each limit mould (side mode) of such multi-wavelength light all equates at interval, and it is the wavelength interval that equates that the opposite side mould carries out that the resulting channel of wavelength separated just becomes.Therefore, such multi-wavelength light, with regard to wavelength configuration, also than use to each channel prepare independent laser and multi-wavelength light that the method for each channel setting wavelength is produced more easy.

Aspect the WDM signal transfer system of realizing the use multi-wavelength light, an important problem is summary and the economization that optical modulating circuit constitutes.Fig. 1 shows the formation of existing optical modulating circuit.The multi-wavelength light that produces from multi wave length illuminating source 101, carried out with wavelength divided device 103 wavelength divided after, modulate with each light intensity modulator 105, close ripple with wavelength wave multiplexer 107 again.In formation shown in Figure 1, owing to must have through equal 2 Wavelength channel join-splitting devices 103,107 of the absolute value of centre wavelength, old friends have proposed 1 Wavelength channel join-splitting device 207 of such usefulness shown in Figure 2, the optic modulating device (opening the 2002-318374 communique referring to the spy) that one or more light intensity modulators 209 and the catoptron 211 that equates with the number of this light intensity modulator constitute.

In optic modulating device shown in Figure 2, import the multi-wavelength light of coming in from the input port 203 of optical input device 201, by input/output port 205 and undertaken by wavelength divided device 207 wavelength divided after, modulate with each light intensity modulator 209, reflect with reflective optical system 211, and return original light path, close ripple with wavelength wave multiplexer 207 once more, from delivery outlet 213 outputs of input-output unit 201.If adopt this device to constitute owing to can only constitute with 1 Wavelength channel join-splitting device 207, so the centre wavelength that sees through of Wavelength channel join-splitting device mate and just become easily, and, all right cutting device cost.

In any one of Fig. 1 and Fig. 2, the luminous power of each wavelength all will reduce because of the loss of employed optical devices such as Wavelength channel join-splitting device.In addition, in the system of the position that multi wave length illuminating source and photomodulator are separated with being in physical property, the loss of the optical fiber transfer path that connects betwixt just becomes and can not ignore.Because the reduction of WDM signal power will cause the deterioration of signal to noise ratio (snr), thus just must with 109 or Fig. 2 of Fig. 1 215 shown in the sort of image intensifer power is amplified.

In Fig. 1 and Fig. 2, the image intensifer that discloses with the broadband of the wave band that covers all multi-wavelength lights amplifies the example (opening the 2003-18853 communique referring to the spy) of WDM signal power together.In this example, use is to amplify its light intensity and the polarized wave of polarized wave that do not rely on the light modulated of wavelength-division multiplex does not have the dependence image intensifer.Such image intensifer generally uses the fiber amplifier of er-doped (Er) fiber amplifier (EDFA) etc.EDFA is to adopt to mix erbium ion Er in the core segment of quartz glass optical fiber ³⁺Way be used in stimulated emission in the intrinsic transition of this ion, be amplified in the image intensifer of the light of advancing in the optical fiber.On the other hand, as the image intensifer that is used for optical communication, developed semiconductor optical amplifier (SOA).SOA is the way that adopts the low reflectionization of resonator end face that makes semiconductor laser, is amplified in the image intensifer of the light of advancing in the active layer in the semiconductor by means of stimulated emission.

No matter above-mentioned any image intensifer, though all be the broadband of gain band more than or equal to 30nm, the life time difference that is positioned at the charge carrier on the excited energy level is very big.EDFA, owing to the transition by means of the excited energy level that comes from a plurality of discretenesses is formed the gain broadening, so carrier life time is long to ms (millisecond) order of magnitude, the gain broadening becomes to inhomogeneous.On the other hand, the carrier life time of SOA is short to ns (nanosecond) order of magnitude, so the gain broadening can be regarded as uniformly.Usually, will be in order to obtain the high power light amplifier in the saturation region operation of gain.In the saturation region of gain, amplifying under a plurality of unlike signal wavelength situations, in the uniform image intensifer of gain broadening, because the contention that each wavelength will gain, produce crosstalking of interchannel and make the signal waveform deterioration.Therefore, under the situation of amplifying the WDM signal, as mentioned above, general is the fiber amplifier that will use EDFA etc. totally.But, as SOA to semiconductor is encouraged, with by the semiconductor laser of output drive light, add and advanced alloy optical fiber such as erbium, when exciting light is coupled to EDFA that the coupling mechanism on the alloy optical fiber constitutes and compares, we can say from the viewpoint of components number and see that SOA is economical.Particularly under the situation of amplifying 1 signal wavelength, this side of SOA is suitable.

Want to amplify the WDM signal together with fiber amplifier, for the loss to the light that produced in the light component parts of Wavelength channel join-splitting device, light intensity modulator etc. compensates, the high powerization of image intensifer is necessary.But, cover the broadband and the high-power image intensifer of the wave band of all multi-wavelength lights, even if for example 1 also be very expensive.Therefore, depend on desired wave band and power, the formation with SOA individually amplifies each wavelength can realize optical modulating circuit more at an easy rate than the formation of using fiber amplifier sometimes.

In addition, SOA also has following advantage.

SOA can be used as modulator by changing injection current according to modulation signal.

SOA can be integrated with the absorption modulator of electric field (EA modulator).

Secondly, the typical configuration example to the optic modulating device that utilizes SOA describes.

(conventional example 1)

Do as conventional example 1, Fig. 3 shows the formation of the existing optic modulating device that can be used in light intensity modulator shown in Figure 1 105.The device of conventional example 1 shows imagination SOA is used as modulator 306, and optic modulating device 303 is in the locational situation of separating with light source.The two ends of the modulator 306 of SOA are coupled on the input transfer path 301 of wanting input optical signal and the output transfer path 309 that will export light signal.But, in these input and output transfer paths, the various optical devices or optical connector, the joint (splice) etc. (not drawing) that also comprise optical filter, photo-coupler etc., in addition, also be inserted with Wavelength channel join-splitting device (not drawing) between the modulator 306 of input and output transfer path 301 and SOA, these component parts all constitute reflection spot.Because these reflection spots are present in the both end sides of the light amplification portion 306 of SOA,, can think that consequently the action of SOA can become unstable so the result just becomes to constituting optical resonator with these reflection spots and SOA.In order to take precautions against this shortcoming, as shown in Figure 3, will insert the optoisolator 305,306 of the light transmission that only makes single direction to the two ends of SOA.

(conventional example 2)

As conventional example 2, Fig. 4 shows the configuration example of the existing optic modulating device that is suitable in the optical modulating circuit of Fig. 2.Figure 4 illustrates the formation of 2 types optic modulating device 405,407.Constituting of 1 type optic modulating device 405: in bidirectional optical amplifier 409, amplify luminous power with the continuous light behind Wavelength channel join-splitting device 403 partial waves, carry out to light intensity modulator 411 input and by means of data-signal after intensity modulated becomes to light modulated, reflect with reflective optical system 413, and then by light intensity modulator 411, bidirectional optical amplifier 409.Constituting of the optic modulating device 407 of another type: in bidirectional optical amplifier 415, amplify luminous power with the continuous light behind Wavelength channel join-splitting device 403 partial waves, to the optical loop input of making of light circulator 417, carry out after intensity modulated becomes to light modulated by means of data-signal in the light intensity modulator 419 in being configured in this optical loop, via light circulator 417, once more by bidirectional optical amplifier 415.In the former optic modulating device 405, both can become the monomer different to reflective optical system 413 with light intensity modulator 411, also can become reflective optical system 413 is pasted incorporate formation on the end face of light intensity modulator 411.

The two-way amplifier 409,415 that in the formation of Fig. 4, uses, as long as owing to can carry out the amplification of a kind of wavelength, so SOA is suitable.But if SOA is used as bidirectional optical amplifier 409,415, then the gain contention between continuous light and the light modulated can cause Signal Degrade in the saturation region of gain.That is, the result becomes to the signal mode at the modulated light of inside continuous light (continuous wave) of image intensifer 409,415 and modulates.

For this reason, as shown in Figure 5, it is desirable to can from the continuous light of bidirectional optical amplifier 409,415 and the output power sum of light modulated (or power input sum) during less than a certain output power (or power input) gain remain in the constant gain unsaturation district and use.

(problem that will solve)

In the formation of conventional example shown in Figure 31,, still can be left problem at the end face reflection of SOA element itself even if inserted optoisolator 305,307 to the two ends of SOA306.Usually, by the end face of SOA306 is carried out the no reflection events coating so that the end face reflection rate reduces, in general, the value of this end face reflection rate is littler than the value of the reflectivity of transfer path reflection etc.But when the gain of SOA306 is big, optic modulating device 303 will become greatly as the effect of resonator, amplify action and just become unstable.That is, the result just becomes the size that value for the end face reflection rate will limit the gain that SOA allows.Therefore, want to realize the high-gain amplification by means of SOA, for example shown in Figure 6, just must couple together SOA multistagely.

As the multistage formation of connecting into of SOA, people have proposed the cascade of SOA+EA modulator (will tell about in the back about the EA modulator) is constituted mode (list of references 1:Ohman, the F. that connects into two-stage; Bischoff, S.; Tromborg, B.; Mork, J.; " Noise properties andcascadability of SOA-EA regenerators ", Lasers and Electro-Optics Society, 2002.LEOS 2002.The 15th Annual Meeting of the IEEE, Volume:2,2002Page (s): 895-896).Be set under the multistage situation at SOA, for the influence that makes light reflection is minimized, though can be as shown in Figure 6 insert optoisolator to the input/output terminal of all SOA of multistage connection, from the viewpoint of cost see then can not say so desirable.In addition, in list of references 1, basic not about inserting telling about of optoisolator.

In addition, in the formation of conventional example shown in Figure 42, exist reflected light 1 and reflected light 2 at the two ends of bidirectional optical amplifier (SOA) 409,415.Although the end face of bidirectional optical amplifier 409,415 is by the low reflectionization of no reflection events coating, still owing to its catoptrical power is exaggerated in the front and back of its end face reflection, so this catoptrical value is big, this reflected light and flashlight are interfered and are become and be noise.In addition, for reflected light 1, reflected light 2, will in the explanation about Fig. 8 described later, explain.

Summary of the invention

The present invention finishes for addressing the above problem, its purpose is to provide a kind of and connects and composes the optic modulating device of image intensifer or contain as bidirectional optical amplifier in the optic modulating device of image intensifer multistage, technical specification design, device by means of the device of the influence of the reflection of considering the inside by image intensifer constitute, and realize reducing catoptrical influence and realize stable enlarging function and economic optic modulating device.

The 1st form of the present invention (aspect) is by the multi-wavelength that combines to the reflective photomodulator that comprises bidirectional optical amplifier with a plurality of these image intensifers optic modulating device together, the relation of the gain of numerical definiteness bidirectional optical amplifier and the loss of image intensifer, reduce the catoptrical influence on the end face of bidirectional optical amplifier, realize stable enlarging function.

The 2nd form of the present invention, by the multi-wavelength that combines to the reflective photomodulator that comprises bidirectional optical amplifier with a plurality of these image intensifers optic modulating device together, carry out the insertion of polarized wave whirligig, reduce the catoptrical influence on the end face of bidirectional optical amplifier, realize stable enlarging function.

The 3rd form of the present invention, whenever insert optoisolator alternately by optic modulating device, to realize simultaneously because of reducing the stable enlarging function that catoptrical influence obtains and the reduction of cost to the through mode that comprises the multistage semiconductor optical amplifier (SOA) that couples together.

Description of drawings

Fig. 1 shows the block diagram of the formation of existing optical modulating circuit;

Fig. 2 shows the block diagram of the formation of existing reflecting light modulating device;

Fig. 3 shows the block diagram of the formation of the existing optic modulating device that utilizes semiconductor optical amplifier;

Fig. 4 shows the block diagram of the formation of the existing optic modulating device that utilizes bidirectional optical amplifier;

Fig. 5 is the curve map in the unsaturation district of explanation semiconductor optical amplifier;

Fig. 6 shows and can regard that multistage connection semiconductor optical amplifier realizes the block diagram of the formation of the optic modulating device that high-gain is amplified as;

Fig. 7 shows the concept map of the catoptrical state (behavior) that a plurality of semiconductor optical amplifiers are multistage when coupling together;

Fig. 8 is the catoptrical concept map of explanation semiconductor optical amplifier;

The concept map of the catoptrical state when Fig. 9 shows 2 multistage coupling together of semiconductor optical amplifier;

Figure 10 is the key diagram of the reflected light of key diagram 9 to the ratio of flashlight;

Figure 11 A-11C is the block diagram of formation that shows the optic modulating device of embodiments of the invention 1 respectively;

Figure 12 A-12C is the block diagram of formation that shows the optic modulating device of embodiments of the invention 2 respectively;

Figure 13 is the curve map of characteristic of the optic modulating device of explanation embodiments of the invention 3;

Figure 14 shows the block diagram of formation of the optic modulating device of embodiments of the invention 4;

Figure 15 is the mode chart of direction on the polarization corrugated of explanation embodiments of the invention 4;

Figure 16 shows the block diagram of formation of the optic modulating device of embodiments of the invention 5.

Embodiment

Below, explain most preferred embodiment of the present invention referring to accompanying drawing.

(embodiment 1)

Embodiments of the invention 1, be to adopt the optic modulating device of the through mode that comprises the multistage semiconductor optical amplifier (SOA) that couples together is inserted the way of optoisolator every 1 ground, realize the embodiment of the reduction of the stable enlarging function that obtains by reducing catoptrical influence and cost simultaneously.Before the concrete configuration example of explanation present embodiment, its principle is described earlier.

＜SOA is multistage when coupling together reflected light 〉

Fig. 7 is explanation the catoptrical figure that a plurality of SOA are multistage when coupling together.In this multistage connecting and composing, in order to make it to play a part optic modulating device, though need or being used as light intensity modulator one of among the SOA that will use, or insertion external modulator, but, make all SOA only play a part image intensifer in order to simplify catoptrical explanation, to be set at here.

In Fig. 7, the semiconductor optical amplifier (S that n (＞=2) is individual ₁, S ₂..., S _i..., S _n) by means of the n+1 that possesses input and output light-path (x ₁, x ₂..., x _i..., x _N+1) in series be coupled, its input and output are connected respectively on input one side transfer path 301, the output one side transfer path 309.As mentioned above, input and output transfer path 301,309 becomes reflection spot.In addition, SOA (S ₁, S ₂..., S _i..., S _n) owing on the two ends of element itself, have reflection end, so SOA self becomes reflection spot.

Fig. 8 is the catoptrical figure of explanation SOA.If establishing the gain of SOA is g _i, the end face reflection rate is r, then when the light of luminous power 1 incides on the SOA, the reflected optical power of SOA just will become and be g _i ²R, the end face reflection rate becomes and is g _i ²Doubly.This reflection can produce on twocouese for each SOA.

In Fig. 7, in order the reflection of the direction identical with the direct of travel of flashlight is decided to be Ref (0) from importing a side, Ref (1) ... Ref (i),, Ref (n) is decided to be ref (1) to backward reflection, ref (2) in order from importing a side, ref (i) ..., ref (n+1).Ref (0) and ref (n+1) are respectively the reflections of input one side transfer path and export side transfer path reflection, reflection Ref (i) in addition and ref (i) expression semiconductor optical amplifier S _iThe reflection of twocouese.

For catoptrical influence, for simplicity, consider the situation of n=2.Fig. 9 be the explanation n=2 situation under catoptrical figure.The unidirectional reflection of direct of travel of Ref (0), Ref (1), Ref (2) expression and flashlight, ref (1), ref (2), ref (3) represent backward reflection.Ref (0) and ref (3) are the reflections of input one side transfer path and export side transfer path reflection that Ref (1), ref (1) and Ref (2), ref (2) are respectively semiconductor optical amplifier S respectively ₁And S ₂Reflection.Why reflection becomes problem in general, be because with the back of the backward reflection of the direct of travel of flashlight (the 1st time reflection), then produce unidirectional reflection (the 2nd time reflection), this reflection and flashlight are interfered to be become signal light power to be unsettled cause.In Fig. 9, owing to comprise the gain of SOA, so reflected light is amplified by this gain, its influence further increases.

Figure 10 be the reflectivity of Ref (i), ref (i) that Fig. 9 is established in explanation when being respectively R (i), r (i) (still, 1＜=i＜=3) 2 secondary reflection light to the table of the ratio of flashlight.As shown in figure 10, then produced in the back of ref (i) under the situation of reflection of Ref (i-1), 2 secondary reflection light are the order of magnitude of 2 powers of the reflectivity of reflection spot to the ratio of flashlight, but produced in the back that is connected on ref (i) under the situation of reflection of Ref (i-2) and even Ref (i-3), 2 secondary reflection light are to the ratio of flashlight, with respect to the order of magnitude of 2 powers of the reflectivity of reflection spot, just will increase the SOA that will pass through gain lucky 2 powers doubly.

Though what Figure 10 illustrated is the situation of n=2, but, in general, n multistage the coupling together of SOA the time, the Ref (i-2) that the back of ref (i) is followed, Ref (i-3), the reflection of Ref (0), the reflection of the Ref (i-1) that follows with the back of ref (i) is compared, and reflected light increases S respectively just to the order of magnitude of the ratio of flashlight _I-1, S _I-1+ S _I-2..., S _I-1+ S _I-2+ ... + S ₁2 powers (wherein, the 1＜=i＜=n+1) doubly of gain.

Therefore, the reflection of the Ref (i-1) that follows for the back that allows ref (i) prevents the Ref (i-2) that the back of ref (i) is followed, Ref (i-3) ..., the reflection of Ref (0) can be to light-path (x ₁, x ₂..., x _i..., X _N+1) whenever insert optoisolator alternately.

＜concrete configuration example 〉

Figure 11 A-11C illustrates as mentioned above the figure of formation of optic modulating device that has whenever inserted the embodiments of the invention 1 of optoisolator for light-path alternately.Here, O ₁, O ₂It is optoisolator.The 1st optoisolator O ₁Be inserted into input one side transfer path and the 1st SOA S ₁Between the 1st light-path x ₁In, the 2nd optoisolator O ₁Be inserted into the 2nd SOA S ₂With the 3rd SOA S ₃Between the 3rd light-path x ₃In.As mentioned above, present embodiment is characterised in that for light-path and whenever inserts optoisolator alternately.

In addition, in this example, the number of SOA is n=3, adopt to use sends signal injection current is carried out the way of intensity modulated, and wherein any one is used as light intensity modulator (MOD).In other words, in Figure 11 A, the 3rd SOA S ₃Be used as light intensity modulator, in Figure 11 B, the 2nd SOA S ₂Be used as light intensity modulator, in Figure 11 C, the 1st SOA S ₁Be used as light intensity modulator.

For the above-mentioned Rankine-Hugoniot relations of optoisolator and light intensity modulator, be 2 situation or for being same more than or equal to 4 o'clock in the number n of SOA.

If adopt the formation of present embodiment, then can the light source of output continuous light and light intensity modulator with transfer path between between mode be arranged in the optical communication system of the position of separating, realize the compensation and the modulation action of the optical power loss of transfer path simultaneously.

(embodiment 2)

Figure 12 A-12C is the figure of formation of the optic modulating device of explanation embodiments of the invention 2.Present embodiment is equivalent to the variation of embodiment 1, to 3 SOA S that constitute image intensifer ₁, S ₂, S ₃In any one between insert light intensity modulator M.

Figure 12 A is not inserting optoisolator O ₁, O ₂The interval in inserted the formation of light intensity modulator M.Here, though what illustrate is to the 1st and 2SOA S ₁, S ₂Between the 2nd light-path (optical connecting device) x ₂In inserted the example of light intensity modulator M, still, also can be to 3SOA S ₃And the 4th light-path x between the lead-out terminal ₄Interpolation is gone into light intensity modulator M.But, in this case, must use can tackle the SOA S that uses afterbody ₃Carried out the light intensity modulator M of the luminous power of amplification.

In the formation of Figure 12 A, from 1SOA S ₁The continuous light and the 2SOA S of output ₂With 1SOA S ₁2 secondary reflection light of continuous light interfere before, receive 2 times intensity modulated with light intensity modulator M.Therefore, 2 secondary reflection light will relatively diminish with respect to the situation of not inserting light intensity modulator M to the ratio of flashlight.

Figure 12 B shows a light intensity modulator M and has been inserted into and has inserted optoisolator O ₂Interval in formation.Here, though what illustrate is to the 2nd and 3SOA S ₂, S ₃Between the 3rd light-path x ₃In inserted the example of light intensity modulator M, still, also can be to input terminal and the 1st SOA S ₁Between the 1st light-path x ₁Interpolation is gone into light intensity modulator M.But, in the latter case, must consider to SOA S ₁The power input of input is because of the loss of light intensity modulator M reduces, the situation of SNR deterioration.In addition, shown in Figure 12 B-12C, optoisolator O ₂With the order that is connected of light intensity modulator M is arbitrarily.

Light intensity modulator M as using in the present embodiment can use for example absorption light intensity modulator of electric field (EA modulator).In the above embodiments 1, because SOA is used as light intensity modulator,, but the EA modulator is being used as under the situation of light intensity modulator so G (bps) or above modulation action are difficult, can tackle the modulation action up to about 40G (bps).

(embodiment 3)

The optic modulating device of embodiments of the invention 3, be to become to make in the device with above-mentioned such bidirectional optical amplifier shown in Figure 4 constitutes, can adopt the way of carrying out the numerical definiteness of Amplifier Gain as described later, reduce the catoptrical influence of the end face of bidirectional optical amplifier, realize the device of stable enlarging function.Below, the numerical definiteness of amplifier gain of the present invention is described.

＜make the catoptrical method that influences quantification 〉

As shown in Figure 4, exist 2 reflected light from the two ends of bidirectional optical amplifier 409,415, a side reflected light 1 is with light modulated and the opposing party's reflected light 2 advances to same direction with continuous light.This continuous light becomes and is light modulated because of carrying out intensity modulated, and reflected light 2 is owing to will experience the path identical with continuous light, so final result is given light modulated reflected light 1 and reflected light 2.The same polarization direction composition of light modulated and reflected light 1 and reflected light 2 is interfered, and produces strength fluctuation as beat noise.Below the method that provides the influence that 2 pairs of light modulated of reflected light 1 and reflected light cause is quantitatively described.

It is contemplated that following situation here.

It is abundant little can ignorance that the repeatedly reflected light that reflects on the end face the opposing party once more at the light after the reflection on a side's of bidirectional optical amplifier 409,415 the end face becomes.

The dutycycle (the empty ratio of mark) that sends signal is 1/2.(because when symbol in the data-signal row or interval consecutive hours, when acknowledge(ment) signal, just be difficult to extract out clock signal, so usually with SDH (synchronous digital hierarchy, SDH (Synchronous Digital Hierarchy)) scrambler in, the 8B → 10B in the Gigabit Ethernet (bel) conversion etc. are adopted dutycycle to be become be 1/2 method substantially).

If poor to the continuous light power of light intensity modulator 411,419 inputs relatively to the gain of the continuous light power of bidirectional optical amplifier 409,415 input, bidirectional optical amplifier 409,415, light modulated output power, the all reflectivity of bidirectional optical amplifier are made as 1 respectively, g, x, r ', and then the light modulated power of photomodulator output, the power of reflected light 1, the power of reflected light 2 just can be used g respectively ²X, r ', g ²x ²R ' expression.

Now, be light modulated and catoptrical interference owing to what become problem, so need only the catoptrical influence when considering the light modulated symbol.Because sending the dutycycle of signal is 1/2, the symbol level power of the light modulated of photomodulator output and the symbol level power of reflected light 2 are respectively 2g ²X, 4g ²x ²R '.But the probability that becomes symbol owing to light modulated and reflected light 2 in photomodulator output simultaneously is 1/2, so the influence of reflected light 2 is halved.Therefore, light modulated during the light modulated symbol and the power ratio between the total reflection light just can be expressed as

$\frac{S}{N}=\frac{2g^{2}x}{(r^{\′}+2g^2{x}^2{r}^{\′})}---\left(1\right)$

In addition, because for r ' r '=g when ignoring optical fiber coupling loss ²The relation of r is set up, so can be rewritten as

$\frac{S}{N}=\frac{2g^{2}x}{(g^{2}r+2g^4{x}^2{r}^{\′})}---\left(2\right)$

If wushu (2) is regarded the function of x as, then exist

$x=\frac{1}{\sqrt{2}g}---\left(3\right)$

The time, formula (2) will be got maximal value.In other words, at this moment can become catoptrical influence and be minimum.If it is rewritten as logarithmically calibrated scale, use transfer path loss L[dB], bidirectional optical amplifier gain G [dB], then become for

$L=-10{\log }_{10}\left(x\right)=10{\log }_{10}\left(g\right)+\frac{1}{2}\·10{\log }_{10}\left(2\right)=G+1.5---\left(4\right)$

In addition, at this moment reflected light 1 becomes to equating with the power of reflected light 2.

In fact because reflected light and light modulated interfere, so above-mentioned in the derivation that makes the optimized following formula of SNR (4), be effective only.Reflected light can carry out as following the estimation of the quantitative property of the influence of light modulated.

Consider to receive the situation of photomodulator output by light circulator 417 grades.If the symbol of light modulated one sidelight electric field is E ₀Exp[i (ω _cT+ φ ₀)], the symbol one sidelight electric field of reflected light 1 is E ₁Exp[i (ω _cT+ φ ₁)], the symbol one sidelight electric field of reflected light 2 is E ₂Exp[i (ω _cT+ φ ₂)], the optical electric field before then receiving just can be used

E _OUT(t)=E ₀Exp[i (ω _cT+ φ ₀)]+E ₁Exp[i (ω _cT+ φ ₁)]+E ₂Exp[i (ω _cT+ φ ₂)] (5) expression.

Receive photocurrent, if when ignoring necessary coefficient fully, then will become for

i _p＝E ₀ ²+2E ₀E ₁exp[i(φ ₀-φ ₁)]+2E ₀E ₂exp[i(φ ₀-φ ₂)]

+ E ₁ ²+ E ₂ ²+ 2E ₁E ₂Exp[i (φ ₁-φ ₂)] (6) here, the 1st is light modulated itself, is noise below the 2nd.The beat (interference) of beat (interference), reflected light 1 power, reflected light 2 power, reflected light 1 and the reflected light 2 of beat (interference), light modulated and the reflected light 2 of the 1st to the 6th light modulated power, light modulated and the reflected light 1 when representing that respectively light modulated and reflected light all are in symbol one side.Because reflected light is little for light modulated, thus the 4th can ignore to the 6th.Here, consider the 2nd with the 3rd influence, as follows as standardization beat noise power definition.

${{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="RIN"\; filenames="A20048000143000291.png,A20048000143000311.png"\; state="\{\{state\}\}">RIN</figure-callout>}}}^2=\frac{2({{\mathrm{<figure-callout\; id="0"\; label="E"\; filenames="A20048000143000291.png,A20048000143000311.png"\; state="\{\{state\}\}">E</figure-callout>}}_0}^2{{\mathrm{<figure-callout\; id="1"\; label="E"\; filenames="A20048000143000291.png,A20048000143000311.png"\; state="\{\{state\}\}">E</figure-callout>}}_1}^2+{{\mathrm{<figure-callout\; id="0"\; label="E"\; filenames="A20048000143000291.png,A20048000143000311.png"\; state="\{\{state\}\}">E</figure-callout>}}_0}^2{{\mathrm{<figure-callout\; id="2"\; label="E"\; filenames="A20048000143000291.png,A20048000143000311.png"\; state="\{\{state\}\}">E</figure-callout>}}_2}^2)}{{\left({{\mathrm{<figure-callout\; id="0"\; label="E"\; filenames="A20048000143000291.png,A20048000143000311.png"\; state="\{\{state\}\}">E</figure-callout>}}_0}^2\right)}^2}---\left(7\right)$

Beat noise under the situation that a plurality of reflection spots participate in can be used as variance and be handled by the Gaussian distribution of the value of formula (7) expression.Otherwise under the few situation of reflection spot, the result just becomes to estimate beat noise superfluously.

Discussion up to now, though what consider as reflected light is reflected light 1 and reflected light 2 from bidirectional optical amplifier 409,415, but, in fact remove outside the end face reflection of bidirectional optical amplifier 409,415, the reflection that also exists the input/output terminal reflection that is inserted into intrasystem various optical devices or produce by optical connector etc., owing to the gain of also accepting bidirectional optical amplifier 409,415 from the reflected light of these reflection spots, just can not ignore again according to their its influence of reflectivity situation.Under these circumstances, if the end face reflection rate r that uses is taken as total from the reflectivity of the reflection spot beyond the end face reflection, we can say that then the estimation of the catoptrical influence of the variance that use is provided by formula (7) is appropriate in discussion up to now.On the other hand, be under the overriding situation in reflection only from the both ends of the surface of bidirectional optical amplifier 409,415, then can regard above-mentioned estimation as the worst design.

Above discussion comes from the IEEE J.lightwave Tchnol. of the method that has provided the influence of estimating array waveguide diffraction grating (AWG) coherent crosstalk quantitatively, vol.14, no.6, pp.1097-1105, the analogizing of 1996 paper.But in this optic modulating device, reflected light 2 is for the probability of prosign is 1/2, so can be rewritten as by wushu (7) during owing to the light modulated symbol

${{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="RIN"\; filenames="A20048000143000291.png,A20048000143000311.png"\; state="\{\{state\}\}">RIN</figure-callout>}}}^2=\frac{2{{\mathrm{<figure-callout\; id="0"\; label="E"\; filenames="A20048000143000291.png,A20048000143000311.png"\; state="\{\{state\}\}">E</figure-callout>}}_0}^2{{\mathrm{<figure-callout\; id="1"\; label="E"\; filenames="A20048000143000291.png,A20048000143000311.png"\; state="\{\{state\}\}">E</figure-callout>}}_1}^2+{{\mathrm{<figure-callout\; id="0"\; label="E"\; filenames="A20048000143000291.png,A20048000143000311.png"\; state="\{\{state\}\}">E</figure-callout>}}_0}^2{{\mathrm{<figure-callout\; id="2"\; label="E"\; filenames="A20048000143000291.png,A20048000143000311.png"\; state="\{\{state\}\}">E</figure-callout>}}_2}^2}{{\left({{\mathrm{<figure-callout\; id="0"\; label="E"\; filenames="A20048000143000291.png,A20048000143000311.png"\; state="\{\{state\}\}">E</figure-callout>}}_0}^2\right)}^2}---\left(8\right)$

The value of this formula equates with 2 times of the inverse of formula (2).

＜about the calculated example of catoptrical influence 〉

Figure 13 shows the result of calculation of using above-mentioned formula (8).In the figure, shown in the transverse axis is modulation portion loss (L) [dB], and it is shown in Q value [dB] and the right side to be optic modulating device gain [dB] that the left side of the longitudinal axis illustrates.For optic modulating device gain, being 2G-L[dB to the modulation loss of the 2G-(L-3.0) [dB] of the modulation loss of not considering the 3dB in the modulation portion (light intensity modulator) 411,419 and consideration 3dB] this two side illustrates.Here said Q value is at IEEE Photon.Technol.Lett.Vol.5, and no.3 puts forward among the pp.304-306, is the evaluating of the signal to noise ratio (snr) of specified modulation light, can by

$Q=\frac{S\left(1\right)-S\left(0\right)}{{\mathrm{\&sigma;}}_1+{\mathrm{\&sigma;}}_0}---\left(9\right)$

Definition.Here, S (1) and S (0) represent symbol and signal level at interval respectively, in addition, and σ ₁And σ ₀Represent symbol and noisiness at interval respectively.Here, if establish S (1)=1, then σ ₁=σ _RIN, S (0) and σ ₀Can be regarded as and be substantially 0.

In calculating, suppose that the continuous light power to optic modulating device 405,407 inputs is-6dBm, bidirectional optical amplifier gain G=10[dB], the bidirectional optical amplifier noise figure is 7dB, the all reflectivity of bidirectional optical amplifier are-22dB, establish directly to carry out receiving light modulated after the light-to-current inversion and do not carry out light preamplifier and receive.Just as its result of calculation of expression shown in Figure 13, modulation portion loss L=11.5[dB], that is, at L=G+1.5[dB] in the Q value get maximal value, the curve of representing the Q value is that the center becomes with this value is left-right symmetric.Among the figure, (α), the scope of (β), (γ), (δ) is as follows respectively.

(α)0＜＝L＜＝2G+3.0

Be to ensure photomodulator gain 2G-[L-3.0]＞=0, and photomodulator gain 2G-[L-3.0]=the modulating sections loss district of the Q value of 0 (dB).

(β)3.0＜＝L＜＝2G

Be to ensure photomodulator gain 2G-L＞=0, and the modulating sections loss district of the Q value of photomodulator gain 2G-L=0 (dB).

(γ)G-4.5＜＝L＜＝G+7.5

Be the Q value with respect to maximal value at 3dB with interior zone.

(δ)L＝G+1.5

It is the modulation portion loss of getting maximum Q value.

For the zone of (δ), situation as mentioned above.In addition, upper limit tables Mingguang City modulation gain of the L in zone (α) and (β) is more than or equal to 0[dB].In addition, for the value of the loss L of light modulated portion, because Q value curve is symmetrical as mentioned above, so can determine inevitably.

In addition, the Q value becomes in the 3dB with respect to maximal value, is at 5.5[dB]＜=L＜=17.5[dB], promptly at (G+1.5)-6[dB]＜=L＜=(G+1.5)+6[dB] in.The scope of this L and the value of G are irrelevant.In fact, if half (minimizing 3dB) of the resulting value in back finds the solution with the 2 power formulas of the x of formula (1) when equating in the above-mentioned formula (1) to the value of the x shown in the above-mentioned formula (3) is updated to, then its separate into

$x=\frac{(2\sqrt{2}\&PlusMinus;\sqrt{6})}{2g}---\left(10\right)$

In addition, when this being separated when being rewritten into logarithmically calibrated scale, just become for

$L=-10{\log }_{10}\left(x\right)=10{\log }_{10}\left(\frac{2}{2\sqrt{2}+\sqrt{6}}\right)+10{\log }_{10}\left(g\right)\&cong;(G+1.5)\&PlusMinus;6---\left(11\right)$

This result shows the higher limit and the lower limit in the zone of (γ).

Therefore, employing makes modulating sections loss L be in way in the scope arbitrarily (for example (β), (γ), (δ)) between the zone of (α), optic modulating device just can keep suppressing lowly under the constant state of gain to the ratio of the relative light modulated of reflected light.At this moment, just as can being recognized by Figure 13, make modulation portion loss L more near the L=G+1.5 of (δ), this ratio is just low more.

(embodiment 4)

Figure 14 shows the formation of the optic modulating device of embodiments of the invention 4.The optic modulating device of present embodiment is a way that adopt to insert the polarized wave whirligig, and the catoptrical influence of lowering the end face of bidirectional optical amplifier realizes the optic modulating device of stable enlarging function.

As shown in figure 14, this device is to possess: the polarized wave separation vessel 501 that separates input multi-wavelength light and output light modulated with the difference on polarization corrugated; The wavelength of each regulation is carried out the Wavelength channel join-splitting device 502 of partial wave to multi-wavelength light; The bidirectional optical amplifier 503 of the power of each single wavelength light after amplifying partial wave on the twocouese; On twocouese, make the polarized wave whirligig 504 of single wavelength polarisation of light corrugated rotation; The light intensity modulator 505 of modulation single wavelength light intensity on twocouese; Make single wavelength light after the modulation of light intensity modulator 505 output return the multi-wavelength optic modulating device together of the reflective optical system 506 of bidirectional optical amplifier 503 once more.

As polarized wave separation vessel 501, though can use the polarized beam beam splitter (PBS) that is often used in general by people, but, for example also can become such formation: output light is exported from Wavelength channel join-splitting device 502 by light circulator or photo-coupler, only takes out and import the light that light has carried out the polarized waves skew of 90 degree with the polarizer.

As Wavelength channel join-splitting device 502, for example can use AWG.AWG makes the light of going into to shine from a certain input waveguide from different output waveguide output according to wavelength.In addition, AWG has reversibility, also can make a plurality of wavelength light close ripple in 1 output waveguide.

As bidirectional optical amplifier 503, for example can use SOA.SOA is the way that adopts the low reflectionization of resonance end face make semiconductor laser, makes the image intensifer that the light of advancing in the active layer in semiconductor amplifies by means of stimulated emission.As bidirectional optical amplifier 503, though also can consider the fiber amplifier of Er-doped fiber (EFDA) etc., but, fiber amplifier because will be with the semiconductor laser of rear pump light, add the additive optical fiber of erbium into etc., the coupling mechanism that pump is coupled light in the additive optical fiber constitutes, event is seen from the viewpoint of components number can expect to become higher than SOA cost, sees that from the cost aspect SOA is favourable.

Though polarized wave whirligig 504 is configured between bidirectional optical amplifier 503 and the light intensity modulator 505,, as this polarized wave whirligig 504, can use 1/4 wavelength plate or faraday components etc.In addition, also can use catoptron has been installed to faraday's catoptron on a side the output terminal of faraday components.

As light intensity modulator 505, can use for example Mach Zehnder type light intensity modulator, electric field absorption-type light intensity modulator (EA modulator) etc., have function with data signal modulation single wavelength light.If adopt these light intensity modulators, then can on practical rank, realize the intensity modulated of carrying out with 40G (bps) order of magnitude modulation signal.

As reflective optical system 507, for example can use and be coated with the catoptron that applies metal film, apply the catoptron etc. of the dielectric multilayer-film that powers on.In addition, as the catoptron of specific wavelength, diffraction grating or Fiber Bragg Grating etc. also can be used as reflective optical system.In addition, as the application examples of Fiber Bragg Grating, also can be that diffraction grating (grating) is directly write to the interior reflective optical system of optical waveguide.

A delivery outlet of polarized wave separation vessel 501 with Space Optical System or optical waveguide optics be connected on the input waveguide of Wavelength channel join-splitting device 502.The output waveguide of Wavelength channel join-splitting device 502 respectively with Space Optical System or optical waveguide optics be connected to bidirectional optical amplifier 503 a side the mouth on.The opposing party of bidirectional optical amplifier 503 the mouth with the same space optical system or optical waveguide optics be connected to polarized wave whirligig 504 a side mouthful on.The opposing party of polarized wave whirligig 504 the mouth with the same space optical system or optical waveguide optics be connected to light intensity modulator 505 a side mouthful on.The opposing party of light intensity modulator 505 the mouth with the same space optical system or optical waveguide optics be connected on the reflective optical system 507.

In the present embodiment, though the input of light intensity modulator 505 and the output of light modulated are cut off with polarized wave separation vessel 501 and are come, but, for example using as polarized wave whirligig 504 under the situation of 1/4 wavelength plate, the angle on input light and output polarisation of light corrugated is owing to carried out 90 degree skews, so as long as only tell the specific polarized wave of exporting light with polarized wave separation vessel 501, input light just can separate with output light.

Multi-wavelength light from the input waveguide of Wavelength channel join-splitting device 502 is imported is into become each wavelength by Wavelength channel join-splitting device 502 partial waves, and the single wavelength light behind the partial wave is led toward 1 corresponding with it bidirectional optical amplifier 503 to amplify its power.

For bidirectional optical amplifier 503, the gain contention in the saturation region of gain between continuous light and the light modulated will cause Signal Degrade.Therefore, in the unsaturation district that keeps gain (longitudinal axis) constant gain, use bidirectional optical amplifier when as shown in Figure 5, it is desirable to from the continuous light of bidirectional optical amplifier 503 and the output power of light modulated (transverse axis) sum (or power input sum) smaller or equal to a certain output power (or power input).

The continuous light (single wavelength light) that has carried out power amplification in each bidirectional optical amplifier 503 is respectively to 504 inputs of corresponding with it polarized wave whirligig.In polarized wave whirligig 504, import continuous lights to light intensity modulator 505, in light intensity modulator 505, carry out intensity modulated by means of modulation signal (data-signal) in polarization corrugated rotation 45 degree backs.Single wavelength light after the modulation is input to reflective optical system 507 from the mouth output of reflective optical system one side of light intensity modulator 505.By the light modulated after reflective optical system 507 reflections, by behind the light intensity modulator 505, be input to polarized wave whirligig 504 once more.Light modulated polarization corrugated in polarized wave whirligig 504 rotates 45 degree once more, and is input to bidirectional optical amplifier 503, carries out luminous power once more and amplify in bidirectional optical amplifier 503.Because the polarization corrugated of the output light modulated of bidirectional optical amplifier 503 has been offset 90 degree with the input light ratio, so can input light be separated with output light by means of polarized wave separation vessel 501.Therefore, the output light modulated of coming out from bidirectional optical amplifier 503 just can be from the delivery outlet of polarized wave separation vessel 501 to the outside output of device after having carried out closing ripple with Wavelength channel join-splitting device 502.

Want to make image intensifer to carry out bidirectional-movement, owing to can not insert optoisolator in the inside of image intensifer, necessary consideration is from the influence of the end face reflection at the two ends in light amplification path.As shown in Figure 4, when two-way transmission, exist 2 these reflected light (reflected light 1 and reflected light 2), reflected light 1 advances on same direction with light modulated, reflected light 2 and continuous light advance on same direction, this continuous light is become light modulated by intensity modulated, reflected light 2 experiences same path with continuous light, so it is same with conventional example, if make reflected light 1,2, continuous light, the polarization corrugated of light modulated becomes and is same direction, then can give light modulated reflected light 1 and reflected light 2, consequently because the same polarization direction composition of light modulated and reflected light 1 and reflected light 2 is interfered and as beat noise generation strength fluctuation.

But, in the formation of present embodiment with polarized wave whirligig 504, shown in the arrow that fences up at the circle of using the direction of representing the polarization corrugated among Figure 15, the reflected light 1 of bidirectional optical amplifier 503 and reflected light 2 are vertical with the polarization direction of continuous light of advancing on same direction or light modulated.Because reflected light 1 is vertical with the light modulated polarization direction, thus in output in polarized wave separation vessel 501 separated coming.In addition, reflected light 2 is vertical with the continuous light polarization direction, carries out intensity transformation afterwards and becomes to keeping this polarization relation after the light modulated, and is same with reflected light 1, also can be in output in polarized wave separation vessel 501 separated coming.Consequently can eliminate by the two-way strength fluctuation that interference of light produced.

In addition, if adopt the formation of present embodiment, as shown in figure 15, owing to reflected in the path that also turns back to once more before coming in the polarized wave whirligig 504 by reflective optical system 507 in output from polarized wave whirligig 504, the polarisation of light corrugated is same person in two-way, pretends the light intensity modulator that only can modulate single input polarization ripple that can use LiNbO3 Mach Zehnder type light intensity modulator etc. for light intensity modulator 505.

(embodiment 5)

Figure 16 shows the formation of the optic modulating device of embodiments of the invention 5.The device of present embodiment 5 is inserted with the polarizer 506 that single polarized wave is passed through front or back (this figure is inserted into the back) of the light intensity modulator 505 of the foregoing description 4 multi-wavelengths optic modulating device together.In addition formation and embodiment 4 are same, its detailed explanation of Therefore, omited.

In general, if a plurality of optical devices or optical fiber are coupled together, the polarized wave extinction ratio between 2 then vertical polarized waves is with remarkable deterioration.If adopt the formation of Figure 16, because the polarisation of light corrugated of being reflected in the path that also turns back to once more before coming in the polarized wave whirligig 504 by reflective optical system 507 from the output of polarized wave whirligig 504 is same person in two-way, so can insert the polarizer 506 in light path.By means of the insertion of this polarizer 506, just can recover deterioration the polarized wave extinction ratio.

(other embodiment)

In addition, though be to be the explanation that example is carried out with the preferred embodiments of the present invention, but, embodiments of the invention are not limited to above-mentioned example, so long as in the described scope of each claim of claim scope, the displacement of its member of formation, change, append, the various distortion of increase and decrease of number, the change of shape etc., all be included in the embodiments of the invention.

Claims (14)

1. optic modulating device is characterized in that possessing:

The continuous light that makes single wavelength sees through and gain is given the bi-directional light multiplying arrangement of this single wavelength light on twocouese;

To having amplified the continuous light of luminous power with above-mentioned bi-directional light multiplying arrangement, with dutycycle substantially 1/2 transmission signal carry out the light intensity modulation device of intensity modulated; With

Make the continuous light that has been carried out intensity modulated by above-mentioned light intensity modulation device return above-mentioned light intensity modulation device once more or directly return the light return device of above-mentioned bi-directional light multiplying arrangement;

Wherein, use with respect to the input of the gain G (dB) of above-mentioned bi-directional light multiplying arrangement toward the luminous power of the input continuous light of above-mentioned light intensity modulation device with from the value of the modulation portion loss L (dB) of the difference definition of the luminous power of the output light modulated of above-mentioned light intensity modulation device, be set to from 0 (dB) in 2G+3.0 (dB) scope.

2. optic modulating device according to claim 1 is characterized in that: the value of above-mentioned modulation portion loss L (dB) is set to G+1.5 (dB).

3. optic modulating device according to claim 1 is characterized in that: above-mentioned bi-directional light multiplying arrangement moves in the unsaturation district of gain.

4. optic modulating device according to claim 2 is characterized in that: above-mentioned bi-directional light multiplying arrangement moves in the unsaturation district of gain.

5. according to any one the described optic modulating device in the claim 1 to 4, it is characterized in that: above-mentioned light intensity modulation device is the reflective light intensity modulator that possesses the reflective optical system that constitutes above-mentioned smooth return device in its back-end.

6. according to any one the described optic modulating device in the claim 1 to 4, it is characterized in that: above-mentioned light intensity modulation device is arranged on the light intensity modulator of formation by the through mode in the optical loop of the above-mentioned smooth return device of light circulator formation.

7. according to any one the described optic modulating device in the claim 1 to 4, it is characterized in that: be provided with the described optic modulating device of reuse wavelengths quantity, also have the continuous light behind the wavelength multiplexing is carried out partial wave and imports respectively and close wave splitter device to carry out wavelength multiplexing and output from the light modulated of a plurality of above-mentioned optic modulating devices outputs to a plurality of above-mentioned optic modulating devices by each single wavelength.

8. an optic modulating device is characterized in that, possesses a plurality of accordingly with each single wavelength light in a plurality of single wavelength light that constitute multi-wavelength light:

Make the single wavelength light that constitutes the described multi-wavelength light that comprises a plurality of light carriers on twocouese, see through and gain is given the bi-directional light multiplying arrangement of this single wavelength light;

The light intensity modulation device that the single wavelength light of having been given gain by above-mentioned bi-directional light multiplying arrangement is seen through on twocouese and this single wavelength light is modulated; And

Make the single wavelength light that has seen through behind the above-mentioned light intensity modulation device return the light return device of this light intensity modulation device once more;

This optic modulating device also possesses:

Above-mentioned multi-wavelength light partial wave become each single wavelength light and respectively to the input of above-mentioned bi-directional light multiplying arrangement, and the wavelength that a plurality of single wavelength light from above-mentioned bi-directional light multiplying arrangement output close ripple and output is once more closed wave splitter device;

Be plugged on a plurality of polarized wave whirligigs that make the rotation of above-mentioned single wavelength polarisation of light corrugated between above-mentioned bi-directional light multiplying arrangement and the above-mentioned light intensity modulation device respectively; With

The polarized wave tripping device, this polarized wave tripping device will be imported multi-wavelength light and be input to above-mentioned wavelength and close wave splitter device, and the output multi-wavelength light that will be by whirligig rotatory polarization corrugated, above-mentioned polarization corrugated closes wave splitter device output from this wavelength separates with above-mentioned input multi-wavelength light and exports.

9. optic modulating device according to claim 8 is characterized in that: also be plugged with the polarizer before or after above-mentioned light intensity modulation device.

10. optic modulating device is characterized in that possessing:

Using independently respectively, injection current produces n (n＞=2) semiconductor optical amplifier that counter-rotating distributes;

(n+1) individual optical connecting device that input terminal and a said n semiconductor optical amplifier and lead-out terminal are coupled together successively;

Be inserted into the odd number of above-mentioned (n+1) individual optical connecting device or the locational optoisolator of even number successively; With

Continuous light is carried out the light intensity modulation device of intensity modulated.

11. optic modulating device according to claim 10, it is characterized in that: this optic modulating device constitutes, to a semiconductor optical amplifier among the said n semiconductor optical amplifier, apply and be sent out the injection current that signal has carried out intensity modulated, and make it become above-mentioned light intensity modulation device.

12. optic modulating device according to claim 10 is characterized in that: any old place that constitutes in above-mentioned (n+1) individual optical connecting device inserts above-mentioned light intensity modulation device.

13. optic modulating device according to claim 10, it is characterized in that: constitute among above-mentioned (n+1) individual optical connecting device, any old place beyond the optical connecting device that is connected with above-mentioned lead-out terminal with above-mentioned input terminal inserts above-mentioned light intensity modulation device.

14. according to claim 12 or 13 described optic modulating devices, it is characterized in that: it constitutes above-mentioned light intensity modulation device is inserted in above-mentioned (n+1) individual optical connecting device and does not insert in the optical connecting device of optoisolator.

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