CN1764864A - Method and device for controlling bias of optical modulator - Google Patents
Method and device for controlling bias of optical modulator Download PDFInfo
- Publication number
- CN1764864A CN1764864A CN 200480008264 CN200480008264A CN1764864A CN 1764864 A CN1764864 A CN 1764864A CN 200480008264 CN200480008264 CN 200480008264 CN 200480008264 A CN200480008264 A CN 200480008264A CN 1764864 A CN1764864 A CN 1764864A
- Authority
- CN
- China
- Prior art keywords
- modulating sections
- low frequency
- photomodulator
- frequency signal
- direct current
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Landscapes
- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Abstract
A method and device for adequately controlling the DC bias of each of the optical modulating sections of an optical modulator even while the optical modulator is operating in normal mode and even with a simple structure. An optical modulator bias controller (B) for controlling the DC bias of each optical modulating section of an optical modulator (1) is characterized by comprising DC bias application means (3) for applying a DC bias to each of the optical modulating sections, a low-frequency signal superimposing circuit (2) for superimposing a low-frequency signal (fB) with a specific frequency on a modulating signal b applied to each optical modulating section, optical sensing means (9) for sensing a change of the intensity of the light wave passing through the combining section, and bias control means (4) for extracting the change of the intensity of light corresponding to the low-frequency signal from the optical sensing means and controlling the DC bias application means according to the extracted change of the intensity of light.
Description
Technical field
The present invention relates to a kind of bias control method and device of photomodulator, be in particular with the photomodulator that inside has a plurality of modulating sections, be used for bias control method that direct current biasing to each modulating sections carries out optimally-controlled photomodulator with and device.
Background technology
Survey the field in optical communication or photometry, adopt photomodulator more as electricity-light conversion element.
As an example of photomodulator, the known LiNbO that utilizes
3(lithium niobate) etc. has the light intensity modulator of the substrate of electric optical effect, yet such photomodulator, applied amount according to the direct current biasing that is used for drive controlling, or according to the temperature variation of environment, the output characteristics of light also can change as time passes, promptly produces so-called drift phenomenon.
Method as the such drift phenomenon of inhibition, following patent documentation 1 or 2 etc. are arranged, make the drive signal of low frequency signal and photomodulator overlapping, light quantity variation in this low frequency signal that is contained from the light of this photomodulator output is monitored, and the actual relatively bias point that applies voltage of detection, and then the bias compensation circuit by combination is controlled the direct current biasing that applies to photomodulator just can carry out making it to become best bias point from normal moveout correction to response characteristics to light.
On the other hand, with the anxious information communication that increases need corresponding, but the optical communication system of a kind of densification of demand, high speed and long-distance transmissions, even demand also can be constructed the DWDM communication system halfway.In this DWDM communication system, need to solve the increase of frequency utilization efficient or the increase problems such as (long distance ionizations) of anti-nonlinear effect, the applicant, (SingleSide-Band, SSB) modulator is as the good modulator of these characteristics to have proposed a kind of one-sided frequency band.
One example of SSB modulator, also on the books in following non-patent literature 1.
Patent documentation 1: the spy opens clear 49-42365 communique;
Patent documentation 2: the spy opens flat 3-251815 communique.
Non-patent literature 1: paper " has adopted X to cut LiNbO
3Light SSB-SC modulator " (day river bend is smoked, other 4, p.17～21 " Osaka, Sumitomo セ メ Application ト テ Network ニ カ Le レ Port one ト version in 2002 ", Osaka, Sumitomo セ メ Application ト Co., Ltd. newly advise skill Intraoperative research institute and put down on Dec 8th, 13)
Principle of work about the SSB modulator describes below.
Fig. 1 represents the SSB modulator, especially carrier suppressed optical SSB (Single Side-Band withSuppressed Carrier, the SSB-SC) mode chart of the optical waveguide of modulator.
At LiNbO
3Form the such optical waveguide of Fig. 1 Deng diffusion backs such as Ti on the substrate with electric optical effect.This optical waveguide has: 2 secondary MZ (Mach-Zehnder) waveguide MZ
A, MZ
BWith main MZ waveguide MZ
CThe arranged side by side master-slave type MZ structure of configuration of each arm.
RF
A, RF
B, for simplification is used for to secondary MZ waveguide MZ
A, MZ
BApply the coplanar electrodes of traveling wave type of microwave modulation signal and graphical sysmbol.And, DC
A, DC
BBe respectively to simplify and give secondary MZ waveguide MZ
A, MZ
BApply the omission graphical sysmbol of the phase place adjustment of the DC voltage that is used to offer the phasing potential difference with electrode; DC
CFor giving main MZ waveguide MZ
CThe phase place adjustment of DC voltage that applies the phase differential that is used to provide given is with the graphical sysmbol of electrode.
Before the work of key diagram 1, earlier the principle about the SSB modulator that do not carry out carrier suppressed describes.Be well known that the SSB modulation technique is a kind of technology in the wireless communication field widespread use,, thereby obtain the SSB modulation signal thus the original signal sum after original signal and the Hilbert conversion.
For carrying out the light SSB modulation of not carrying out carrier suppressed, as long as adopt the so two independent MZ modulators (illustrating an example of utilizing Z to cut substrate) that drive of Fig. 2.
Will be as the incident light of exp (j ω t), from RF
APort input single-frequency RF signal psi cos Ω t, and, simultaneously respectively from RF
BPort input is carried out signal H[φ cos Ω t after the Hilbert conversion to this signal]=φ sin Ω t.
According to sin Ω t=cos (Ω t-pi/2),, just can provide 2 signals simultaneously by the phase-shifter that utilizes microwave to use.Wherein, φ represents degree of modulation, and ω, Ω represent each frequency of light wave and microwave (RF) signal respectively.
Also have from DC
AAfter the additional suitable biasing of port, the phase differential pi/2 is provided for the light wave of two arms by the MZ waveguide.
Like this, focus on the phase term of the light wave in ripple stack place, can represent by following formula (1).
exp(jωt)*{exp(jφcosΩt)+exp(jφsinΩt)*exp(jπ/2)}＝2*exp(jωt)*{J
0(φ)+j*J
1(φ)exp(Ωt)} ……(1)
Here, J
0, J
1Be 0 time, 1 time Bessel function, the composition below 2 times can be ignored.
Suc as formula (1), though that the wave spectrum composition of 0 time and 1 time also has is remaining ,-1 composition (J
-1) removed (if by shown in the pattern, being the light wave that distributes at wave spectrum such shown in the right side of the MZ of Fig. 2 waveguide) fully from the emission of secondary MZ waveguide.
And, about remaining-1 composition (J
-1), in order to remove composition (J 1 time
1), by imposing on DC
APort provides the biasing of phase place-pi/2 just can realize.
Then, under the situation of carrier suppressed optical SSB (SSB-SC) modulator, as shown in Figure 1, in two arms of independent MZ EVAC (Evacuation Network Computer Model), setting has secondary MZ EVAC (Evacuation Network Computer Model).
Give this secondary MZ waveguide, apply so as shown in Figure 3 signal.This also can think and normal intensity modulated be carried out the identical situation of bottom (bottom) driving.
At this moment, focus on radiative phase term, then represent by following formula (2).
exp(jωt)*{exp(jφsinΩt)+exp(-jφsinΩt)*exp(jπ)}＝2*exp(jωt)*(J
-1(φ)exp(-jΩt)+J
1(φ)exp(jΩt)} ……(2)
Like this, the even number time wave spectrum composition that contains the carrier wave composition as can be known has been eliminated (from the pattern expression, be the light wave that distributes at wave spectrum such shown in the right side of the MZ of Fig. 3 waveguide and penetrate) from secondary MZ waveguide.
And the carrier suppressed method by making up above-mentioned SSB modulation (formula (1), shown in Figure 2 modulation system) and secondary MZ (formula (2), shown in Figure 3 modulation system) just can optionally only produce 1 time wave spectrum (J
1Item) ,-1 wave spectrum (J
-1Item) certain in-individual.
Like this, the SSB modulator can utilize the wavelength shifter as light wave, and especially, the SSB-SC modulator can suppress the generation of 0 wave spectrum, and efficiently produces 1 time or-1 wave spectrum.
As shown in Figure 1, with making up the photomodulator of the shape of 3 MZ waveguides, especially be called nested (nest) type light intensity modulator (OSSB, Optical Single Side-Band Modulator).
Like this, though proposed various with in 1 photomodulator of a plurality of modulating sections embeddings, just can realize the photomodulator of multifunction, high performance, yet it is as above-mentioned, utilization has the photomodulator of the substrate of electric optical effect, owing to there is drift phenomenon common inherence, therefore need proofreaies and correct, and guarantee to drive bias point for suitable to the direct current biasing that drives modulating sections.
Suppose, if adopt the inhibition method of the relevant drift phenomenon of above-mentioned photomodulator, then for example under the situation of the nested light intensity modulator of Fig. 1, need be to 3 direct current biasing DC
A, DC
B, DC
CControl.Yet, for to DC
A, DC
BProofread and correct control, just need be provided with separately passing through secondary MZ
A, MZ
BThe testing agency detected of light wave, even under the situation of not proofreading and correct control, for example to DC
AWhen controlling, need be to making other the (MZ of MZ portion
B, MZ
C) be made as off working state etc. and control.
Like this, increase along with modulating sections, formation in the direct current biasing control of photomodulator can be complicated, and, for measuring the input-output characteristic of specific modulating sections, other modulating sections is made as produces so imappropriate situation of not proofreading and correct when off working state etc., normal optical communication or photometry are surveyed.
Summary of the invention
The object of the present invention is to provide a kind of, address the above problem, for photomodulator with a plurality of modulating sections, also can be with simple structure, and in the operate as normal of photomodulator, the bias control method of the photomodulator that the direct current biasing of each modulating sections is suitably proofreaied and correct with and device.
For solving above-mentioned problem, one of the present invention is a kind of bias control method of photomodulator, for by having the optical waveguide that forms on the substrate of electric optical effect; Be used for a plurality of modulating sections that the light wave of propagating at this optical waveguide is modulated; Carry out the photomodulator that the ripple stack constitutes with the light wave after will modulating by these a plurality of modulating sections, the direct current biasing in these a plurality of modulating sections will be controlled.It is characterized in that, make low frequency signal overlapping with modulation signal or the direct current biasing of applying for these a plurality of modulating sections with characteristic frequency, detecting the light quantity corresponding with this low frequency signal according to the light wave after this ripple stack changes, and change based on the light quantity of this detection, the direct current biasing of each modulating sections is controlled.
And the present invention's two is a kind of bias control methods according to one of invention described photomodulator, it is characterized in that, the frequency that this is specific is for pressing the different frequency of each modulating sections.
Also have, the present invention's three is bias control methods of a kind of two described photomodulators according to invention, it is characterized in that the frequency that these are different, the mode that doubly concerns with mutual an odd lot and constituting.
In addition, the present invention's four is a kind of bias control methods according to one of invention described photomodulator, it is characterized in that the overlapping moment of this low frequency signal is, by carrying out with the different moment in each modulating sections.
Further, the present invention's five is bias control methods of a kind of photomodulator, is for by having the optical waveguide that forms on the substrate of electric optical effect; Be used for a plurality of modulating sections that the light wave of propagating at this optical waveguide is modulated; Carry out the ripple stack and the control method of the photomodulator that constitutes with making by the light wave after this a plurality of modulating sections modulation, it is characterized in that, make low frequency signal with characteristic frequency, overlapping with modulation signal or direct current biasing that at least 1 modulating sections of giving in these a plurality of modulating sections applies, according to from applying the light wave of the modulating sections emission that makes overlapping modulation signal of this low frequency signal or direct current biasing, the light quantity variation corresponding with this low frequency signal detected, and change based on the light quantity of this detection, the direct current biasing of modulating sections whole or a part of in these a plurality of modulating sections is controlled.
Also have, the present invention's six, it is a kind of bias control method of five described photomodulators according to invention, it is characterized in that, being controlled to be of the direct current biasing of the whole or a part of modulating sections in these a plurality of modulating sections, change decision and the control controlled quentity controlled variable corresponding with each modulating sections based on this light quantity.
More have, the present invention's seven is bias controllers of a kind of photomodulator, by the substrate with electric optical effect; With the optical waveguide that on this substrate, forms; Be used for a plurality of modulating sections that the light wave of propagating at this optical waveguide is modulated; Be arranged on the photomodulator that optical superposition portion that the light wave that is used for that this a plurality of modulating sections is modulated carries out this optical waveguide of ripple stack constitutes, be used for the direct current biasing of these a plurality of modulating sections is controlled.It is characterized in that, comprise: the direct current biasing applying mechanism, it applies direct current biasing to these a plurality of modulating sections; The low frequency signal superposing circuit, it makes the low frequency signal with characteristic frequency overlapping with modulation signal or the direct current biasing of applying for these a plurality of modulating sections; Light detecting mechanism, its light quantity to the light wave by this ripple stack portion change and detect; With the biasing control gear, it extracts the light quantity variation corresponding with this low frequency signal out from this light detecting mechanism, and the light quantity based on this extraction changes simultaneously, and this direct current biasing applying mechanism is controlled.
And the present invention's eight is bias controllers of a kind of seven described photomodulators according to invention, it is characterized in that, this low frequency signal superposing circuit has correspondingly with each modulating sections, produces a plurality of low frequency signal generating units of low frequency signal.
Also have, the present invention's nine, it is a kind of bias controller of seven described photomodulators according to invention, it is characterized in that, this low frequency signal superposing circuit, have 1 the low frequency signal generating unit that produces low frequency signal, and will offer each modulating sections from the low frequency signal switching of this low frequency signal generating unit.
Also have, the present invention's ten is bias controllers of a kind of photomodulator, for by the substrate with electric optical effect; The optical waveguide that on this substrate, forms; Be used for a plurality of modulating sections that the light wave of propagating at this optical waveguide is modulated; The photomodulator that the ripple stack portion that makes light wave by these a plurality of modulating sections modulation carry out the ripple stack with being used to of being provided with in this optical waveguide constitutes is used for the direct current biasing of these a plurality of modulating sections is controlled.It is characterized in that, comprise: the direct current biasing applying mechanism, it is used for these a plurality of modulating sections are applied direct current biasing; The low frequency signal superposing circuit, it makes the low frequency signal with characteristic frequency overlapping with modulation signal or direct current biasing that at least 1 modulating sections of giving in these a plurality of modulating sections applies; Light detecting mechanism, it changes the light quantity corresponding with this low frequency signal and detects by from applying the light wave of the modulating sections emission that makes overlapping modulation signal of this low frequency signal or direct current biasing; The biasing control gear, it extracts the light quantity variation corresponding with this low frequency signal out from this light detecting mechanism, and the light quantity based on this extraction changes simultaneously, and the direct current biasing applying mechanism of the whole or a part of modulating sections in these a plurality of modulating sections is controlled.
In addition, the present invention's 11, be a kind of according to seven of invention～the bias controller of ten each described photomodulators, it is characterized in that this light detecting mechanism detects the light wave of radially launching in this substrate from this optical waveguide.
The present invention's 12, be a kind of according to seven of invention～the bias controller of ten each described photomodulators, it is characterized in that, this light detecting mechanism, it detects the light wave of being derived by near the directional coupler that is configured in this optical waveguide.
The present invention's 13, be a kind of according to seven of invention～the bias controller of ten each described photomodulators, it is characterized in that this optical detection device adopts dropinsert equipment structure light wave along separate routes to detect to the light wave from this photomodulator emission.
The present invention's 14, be a kind of according to 11 of invention～the bias controller of 13 each described photomodulators, it is characterized in that this light detecting mechanism has the photodetector more than at least 2.
1 the invention according to the present invention by applying specific low frequency signal to each modulating sections, and changes its corresponding light quantity and to detect, and so just can hold the situation relevant with the drift phenomenon of each modulating sections easily.And, photomodulator and bias control circuit are oversimplified, even and when utilizing photomodulator, also can control to the direct current biasing of each modulating sections.
Two invention according to the present invention, just can be by each frequency signal corresponding with each modulating sections, hold the situation relevant with the drift phenomenon of each modulating sections, and, owing to the frequency difference of the low frequency signal of applying for each modulating sections, therefore also can grasp the movement of a plurality of modulating sections simultaneously.
When holding the state of the drift phenomenon in a plurality of modulating sections at the same time, under the situation of relation that between the different frequencies is mutual integer multiple frequency, may produce so improper situation: promptly the input-output characteristic that produces because of the low frequency signal of applying for other modulating sections changes, and also may detect simultaneously as the characteristic of the modulating sections of paying close attention to.According to three invention of invention, just can eliminate so imappropriate situation.
Four invention according to the present invention even be a kind or seldom under the situation of kind in the frequency of low frequency signal, is staggered by making the overlapping moment, also can control the biasing of most modulating sections.
Five invention according to the present invention, apply specific low frequency signal at least 1 modulating sections in these a plurality of modulating sections, detect by the light wave pair light quantity corresponding variation with this low frequency signal from this modulating sections emission, and change based on the light quantity of this detection, not only, also the direct current biasing of other modulating sections is controlled this modulating sections.Like this, the overlapping or output light-wave of the low frequency signal of each modulating sections correspondence is detected, can make the simplification that becomes of all structures of photomodulator, and the direct current biasing of each modulating sections is controlled made it to become appropriate state easily with regard to not needing respectively.And,, also can control the direct current biasing of each modulating sections even when utilizing photomodulator.
By by the design of photomodulator or the characteristic measurement of each photomodulator etc., be predetermined the correlationship of the drift phenomenon of the modulating sections that applies low frequency signal and other modulating sections, and change based on the light quantity of the modulating sections that applies low frequency signal, determine the controlled quentity controlled variable of each modulating sections with reference to described correlationship.Then, according to six of invention, not only measure the drift phenomenon of a part of modulating sections, the controlled quentity controlled variable that can also keep each modulating sections is suitably, can suppress the complicated of control function in the photomodulator, even and when utilizing photomodulator, also can efficiently control.
According to seven of invention, same with one of invention, apply specific low frequency signal for each modulating sections, and change by detecting its corresponding light quantity, just can hold the situation relevant easily with the drift phenomenon of each modulating sections.And, photomodulator and bias control circuit are oversimplified, and, even when utilizing photomodulator, also can control the direct current biasing of each modulating sections.
Especially, according to eight of invention, frequency difference owing to the low frequency signal of applying for each modulating sections, therefore can grasp the movement of a plurality of modulating sections simultaneously, and, according to nine invention of invention, even be under the situation of a kind in the frequency of low frequency signal, by alternately providing low frequency signal, just can control the biasing of most modulating sections to each modulating sections.
According to the present invention ten, with invention five or six same, do not need the overlapping or output light-wave of the low frequency signal corresponding with each modulating sections is detected, can make the simplification that becomes of all structures of photomodulator, and can control the direct current biasing of each modulating sections easily and make it to become appropriate state.And,, also can control the direct current biasing of each modulating sections even when utilizing photomodulator.And the correlationship of the drift phenomenon by being predetermined the modulating sections that applies low frequency signal and other modulating sections according to the setting adjustment of biasing control gear, just can suitably be controlled the direct current biasing of each modulating sections.
In the photomodulator, wait until in the substrate from the ripple stack of optical waveguide, emission is called the light wave of being confused light, 11 invention according to invention, by effectively utilizing this light wave, can prevent the deterioration of flashlight with regard to not needing to direct or its a part of detection of flashlight from the photomodulator emission.
12 invention according to invention utilizes directional coupler, just can detect at the local light wave of propagating in to the optical waveguide in substrate arbitrarily.And, directional coupler, owing to can by with substrate on optical waveguide be that identical flow process forms, therefore can form simultaneously with optical waveguide.
According to 13 invention of invention, because the light signal from the photomodulator emission is directly detected, therefore can correctly hold the input-output characteristic of all or each photomodulator of photomodulator.And, even be difficult to dispose under the situation of photodetector near the photomodulator, will be in the light paths such as optical fiber that derive the outside by the light of photomodulator emission, by adopting waveguide or dropinsert equipment structures such as polarizing beam splitter, photo-coupler along separate routes, just can carry out light and detect the optional position.
According to invention 14 invention, corresponding with a plurality of modulating sections, by a plurality of photodetectors are set, just can cut down the quantity of the modulating sections that 1 detecting device bears.Therefore,, therefore also can enlarge the range of choice of this frequency, alleviate the burden of the circuit of extracting the light quantity variation corresponding out simultaneously with each low frequency signal owing to can select to be suitable for the photodetector of the frequency of low frequency signal.
Description of drawings
Fig. 1 represents the skeleton diagram of SSB modulator.
Fig. 2 represents the figure of effect of the main MZ waveguide of SSB modulator.
Fig. 3 represents the figure of effect of the secondary MZ waveguide of SSB modulator.
Fig. 4 represents the skeleton diagram of the bias controller of photomodulator of the present invention.
Fig. 5 represents the figure of applying method one example of low frequency signal of the present invention.
Fig. 6 represents the figure of light detection method one example of the present invention.
Fig. 7 represents the figure of another example of light detection method of the present invention.
The figure of the control method that the state that Fig. 8 represents the modulating sections of a part according to the present invention is controlled other modulating sections.
Embodiment
Below, the present invention is described in detail to adopt preferred example.
Fig. 4 is the skeleton diagram of an embodiment of the bias controller of photomodulator of the present invention.
Below, be that example describes with regard to the nested light intensity modulator, but the present invention is not limited to this, if be the photomodulator that a plurality of modulating sections of combination (part with intensity modulation function or phase modulation (PM) function) constitute, then also be suitable for the present invention.
In photomodulator 1, form secondary MZ type optical waveguide MZ
A, MZ
B, and main MZ type optical waveguide MZ
C, by the various modulator electrodes of corresponding setting, form a plurality of modulating sections simultaneously with this optical waveguide.
For example, at MZ
AModulating sections in, apply modulation signal RFA and dc offset voltage DC
A, carry out optical modulation for example shown in Figure 3.
MZ
BModulating sections, basically with MZ
AEqually, and, at MZ
CModulating sections in, by according to dc offset voltage DC
CApply given phase differential and constitute
Bias controller about photomodulator carries out diagrammatic illustration.
If pay close attention to secondary MZ type optical waveguide MZ
B, 2 for making low frequency signal f
BB is overlapping with modulation signal, has the low frequency superposing circuit of the function that makes the modulation signal amplification simultaneously.The output of low frequency superposing circuit 2 is as modulation signal RF
B, impose on secondary MZ type optical waveguide MZ
B, and carry out given modulation for the light wave of in this optical waveguide, propagating.3 for direct current biasing applies circuit, and to secondary MZ type optical waveguide MZ
BApply given dc offset voltage DC
B
At secondary MZ type optical waveguide MZ
BIn the light wave propagated, at main MZ type optical waveguide MZ
CRipple stack portion in, and at the opposing party's secondary MZ type optical waveguide MZ
AMiddle light wave phase mutual interference of propagating, and from photomodulator 1, make the emission light wave and penetrate.
The part of this emission light wave by photo-coupler 12, is gone into directive photodetector 9.Photodetector 9, output changes corresponding signal with light quantity, by low frequency signal composition detection circuit 5, the low frequency signal f that contains in the output signal to photodetector 9
BLight quantity change and to detect, and output to bias control circuit 4.In addition, to low frequency signal composition detection circuit 5, apply low frequency signal f as contrast signal
B
In the bias control circuit 4, as the spy before open clear 49-42365 communique, the spy opens shown in the flat 3-251815 communique, according to the value that the light quantity in the low frequency signal changes, obtains best dc offset voltage DC
B, and direct current biasing is applied circuit 3 control.
The area surrounded B of dotted line institute of Fig. 4, vice MZ type optical waveguide MZ
BCorresponding biasing control gear.And regional A represents same MZ type optical waveguide MZ
ACorresponding biasing control gear.
If focus on main MZ type optical waveguide MZ
C, then, apply as dc offset voltage DC to bias control circuit 7 indications
CThe initial value of voltage, and input signal c.This bias control circuit 7 is corresponding with this input signal c, direct current biasing is applied circuit 6 control, and given voltage is offered DC
CAlso have, apply circuit 6 input low frequency signal fc, and will make this low frequency signal and offer DC with the corresponding voltage of voltage after overlapping that applies of bias control circuit 7 to direct current biasing
C
If make input signal c change, then will make low frequency signal with and the overlapping dc offset voltage of the corresponding given voltage of this signal c offer DCc, and at main MZ type optical waveguide MZ
CThe middle light wave of propagating provides with this and applies the corresponding given phase differential modulation of voltage.
The light wave of propagating in main MZ optical waveguide MZc after accepting above-mentioned phase modulation (PM), is launched by photomodulator 1, and is outputed to the outside as light signal.
The part of emission light wave, by photo-coupler 12, photodetector 9 is given in incident as above-mentioned, and by low frequency signal composition detection circuit 8, the light quantity variation of the low frequency signal fc that contains in the output signal to photodetector 9 detects, and outputs in the bias control circuit 7.In addition, give low frequency signal composition detection circuit 8, apply low frequency signal fc as contrast signal.
In the biasing control short circuit 7,, obtain best dc offset voltage DC according to the value that the light quantity in the low frequency signal changes
C, and direct current biasing is applied circuit 6 control.
The area surrounded C of dotted line institute of Fig. 4 represents main MZ type optical waveguide MZ
CCorresponding biasing control gear.
Then, the bias control method to the bias controller that adopts above-mentioned photomodulator describes.
If to photomodulator 1 input incident light wave, then light wave is shunted to secondary MZ type optical waveguide MZ in the photomodulator 1
A, MZ
BSecondary MZ type optical waveguide MZ
BIn, according to making low frequency signal f
BModulation signal RF with input signal b after overlapping
B, the light wave of propagating is modulated.On the other hand, secondary MZ type optical waveguide MZ
AIn too, according to making low frequency signal f
AThe modulation signal RF overlapping with not shown input signal a
A, the light wave of propagating is modulated.
By the light wave of 2 secondary MZ type optical waveguide modulation, by main MZ type optical waveguide MZ
C, given phase differential is provided, and exports as light signal from photomodulator 1.In addition, this phase differential, with make low frequency signal fc with and the corresponding overlapping dc offset voltage DC of given voltage of input signal c
CCorresponding.
From the light wave of photomodulator 1 emission, by photo-coupler 12, its a part of incident is to photodetector 9.The output of photodetector is input to biasing control gear A, B, C respectively.And the order by the above-mentioned control gear of respectively setovering, to dc offset voltage DC
A, DC
B, DC
CControl.
Being characterized as of present embodiment, each biasing control gear A, B, C are by utilizing specific low frequency signal f
A, f
B, f
C, by according to MZ as each modulating sections
A, MZ
B, MZ
CIn the optical modulation carried out of each low frequency signal and change according to the output signal pair light quantity corresponding of photodetector with this low frequency signal detect, just can correctly grasp the state of each modulating sections.
Therefore,, adopt extremely low frequency signal in the back, also can ignore influence, and can carry out biasing control modulating sections to communication by frequency ratio with this signal of communication even during in proper communication etc., utilizing photomodulator.
Precision when extracting the signal content that detects each low frequency signal for improving out from the output signal of photodetector, the frequency of preferred low frequency signal are whole different frequencies.Especially, as if relation, not the relation of mutual integral multiple according to each frequency, set the frequency of low frequency signal, then can realize better detection performance.
And, as Fig. 5, utilize 1 low frequency signal f, by output switching mechanism 20, just can switch successively and utilizes the low frequency signal that applies to the control gear A that setovers, B, C at given time.
In this case, each control gear of setovering, it constitutes, and only carries out work when the input low frequency signal, and implements above-mentioned biasing control.
Then, state about other example of light detection method of the present invention.
Fig. 6 is for adopting waveguide or dropinsert equipment structures such as polarizing beam splitter, photo-coupler 30,31,32 along separate routes, with a part of direct light detecting device 33,34,35 of emission light wave.Like this, by the light signal from photomodulator emission is directly detected, just can correctly hold photomodulator all or the input-output characteristic of each modulation portion.And, even be difficult under near the situation of the configuration photodetector photomodulator, via with the emission photoconduction of photomodulator to the optical fiber of outside etc., by adopting the dropinsert equipment structure halfway, also can carry out light at an arbitrary position and detect.
And because each biasing has photodetector 33～35 in control gear, the modulating sections that 1 photodetector should be shared also is 1, and can select the photodetector of the frequency that is suitable for low frequency signal.Therefore, can enlarge the range of choice of this frequency, can also alleviate simultaneously and extract the circuit burden that the light quantity corresponding with each low frequency signal changes out.
Also have, among Fig. 7 (a), expression is as the light wave (fan's light) 40 that will radially be launched in the substrate by optical waveguide, the light detection method that detects by photodetector 41.Like this, in the photomodulator, from emission fan light in substrate such as the ripple stack portion of optical waveguide, by effectively utilizing this fan's light, with regard to not needing the flashlight from the photomodulator emission is directly detected or its part is detected, can prevent the deterioration of flashlight.
Also have, Fig. 7 (b) expression detects by 51 pairs of light waves of being derived by near the directional coupler 50 that is configured in optical waveguide of photodetector.Photodetector 52, the state that is used for light wave that biasing control gear A, C are adopted detects.
Like this, utilize directional coupler etc., just can detect at any local light wave of propagating in to the optical waveguide in substrate.And, directional coupler, because can be by forming with the same technology of the optical waveguide on substrate, formation can form simultaneously with optical waveguide.
Such light detection method, for in the emission light wave pair situation that the signal corresponding with the state of this modulating sections detects that is difficult to according to photomodulator, or want from the light quantity of all emission light waves of photomodulator changes, to remove the situation etc. of the influence of this modulating sections, all be unusual effective method.
Secondly, about measuring the drift phenomenon of at least 1 modulating sections in a plurality of modulating sections, the control method of correction that its result is suitable for the direct current biasing of other modulating sections describes.
Modulating sections in a situation that embeds a plurality of modulating sections on the same substrate and the part in these a plurality of modulating sections produces under the situation of drift phenomenon, and usually, the possibility that produces drift phenomenon in other the modulating sections too is higher.And, the generation of this drift phenomenon tendency, because be at same substrate, and owing to the generation reason of the drift phenomenons such as temperature variation of substrate is also identical, therefore the state variation that produces because of drift phenomenon has similar tendency.Especially, in contiguous other modulating sections of measuring the modulating sections configuration that light quantity changes, or between the modulating sections as SSB modulator balanced configuration modulating sections, also have and be inclined to like the state class of drift phenomenon.
Utilize above-mentioned characteristic, measure the drift phenomenon at least 1 modulating sections in a plurality of modulating sections,, and other the direct current biasing of modulating sections controlled with reference to its measurement result.
As concrete example, Fig. 8 (a) and (b) are represented the result that measured in the specific modulating sections, are suitable for the example of other modulating sections.
Fig. 8 (a) expression is according to secondary MZ
AModulating sections in the drift phenomenon measured, not only to secondary MZ
A, also to secondary MZ as other modulating sections
BOr main MZ
CThe method of controlling.
At first, make low frequency signal and secondary MZ
AModulating sections overlapping, read from this modulating sections MZ by directional coupler 60
AThe part of the light wave of emission will be input to biasing control gear 62 by the light signal 61 that not shown photodetector detects as above-mentioned.
In the biasing control gear 62, measure the light quantity corresponding and change, and judge secondary MZ with overlapping low frequency signal
AThe state of the middle drift phenomenon that produces will be to secondary MZ
AThe direct current biasing DC that applies
ABe set at appropriate value.
And, in the biasing control gear 62, about secondary MZ
BAnd main MZ
C, based on vice MZ
AThe above-mentioned light quantity of drift phenomenon change, with each direct current biasing DC
B, DC
CBe set at appropriate value.
For example, because secondary MZ
AWith secondary MZ
BBe the shape of symmetry, so the correcting value of direct current biasing too, about main MZ
C, it constitutes can measure secondary MZ in advance
ADrift phenomenon and main MZ
CThe correlationship of drift phenomenon, and, calculate main MZ based on its correlationship
CDirect current biasing DC
CAppropriate value.
The controlled quentity controlled variable of direct current biasing, shape according to modulating sections, can change because of various factorss such as the state of substrate, environments for use, therefore in design phase of photomodulator, under situation about can predict in advance in the correlationship of the drift phenomenon between the modulating sections that photomodulator is embedded in, above-mentioned biasing control gear 62, can set based on its correlationship, yet the product at each photomodulator all exists under the situation of scattered error etc., preferably by each photomodulator, set correlationship, perhaps the setting value of predefined correlationship is proofreaied and correct.
Fig. 8 (b) expression is according to secondary MZ
AModulating sections in the drift phenomenon measured, to secondary MZ
AAnd secondary MZ
BThe method of controlling.
In addition, among Fig. 8 (b), setting the light wave that obtains from directional coupler 70 is to launch to the optical axis approximate vertical direction of relative all photomodulators.Like this, according to the configuration of photodetector, or contain the formation configuration of all devices of photomodulator, the emission part of directional coupler can be set in the optional position on the substrate.
Secondary MZ
AAnd secondary MZ
BControl method, basic and Fig. 8 (a) are equally.Emission light from directional coupler 70 imports not shown photodetector, and will be input to biasing control gear 71 from the light signal of this photodetector.Then, in the biasing control gear 71, set direct current biasing DC
A, DC
BBe optimum value, and control.
On the other hand, about main MZ
C, control according to different biasing control gears 72.
The present invention, be not limited to above explanation, for example, be not limited on single substrate, form above-mentioned a plurality of modulating sections, also can comprise a plurality of photomodulators of combination, constitute the photomodulator that has as all a plurality of modulating sections, and, also be not limited to all light waves of a plurality of modulating sections are synthesized, also only can comprise a part of light wave is synthesized.Also have, in not breaking away from purpose scope of the present invention, also can be included in the additional known technology of this technical field.
As mentioned above, according to the present invention, even provide a kind of for modulator with a plurality of modulating sections, also can be with simple structure, and in the operate as normal of photomodulator, also the bias control method of the photomodulator that can suitably proofread and correct the direct current biasing of each modulating sections with and device.
Claims (14)
1, a kind of bias control method of photomodulator, photomodulator has the optical waveguide that forms on the substrate of electric optical effect; Be used for a plurality of modulating sections that the light wave of propagating at this optical waveguide is modulated; And make by the light wave after this a plurality of modulating sections modulation and carry out the ripple stack, the direct current biasing in these a plurality of modulating sections is controlled, it is characterized in that, comprise:
Make low frequency signal with characteristic frequency, superimposed with modulation signal or the direct current biasing of applying for these a plurality of modulating sections;
Detect by pair light quantity corresponding variation of the light wave after this ripple stack with this low frequency signal;
Light quantity based on this detection changes, and the direct current biasing of each modulating sections is controlled.
2, the bias control method of photomodulator according to claim 1 is characterized in that,
The frequency that this is specific is for according to the different frequency of each modulating sections.
3, the bias control method of photomodulator according to claim 2 is characterized in that,
The frequency that these are different is made of the frequency that does not become the integral multiple relation mutually.
4, the bias control method of photomodulator according to claim 1 is characterized in that,
Make the overlapping moment of this low frequency signal, in each modulating sections, carrying out with the different moment.
5, a kind of bias control method of photomodulator, photomodulator has the optical waveguide that forms on the substrate of electric optical effect; Be used for a plurality of modulating sections that the light wave of propagating at this optical waveguide is modulated; Light wave by these a plurality of modulating sections modulation carries out the ripple stack, and the direct current biasing in these a plurality of modulating sections is controlled, and it is characterized in that, comprises:
Make low frequency signal with characteristic frequency, overlapping with modulation signal or direct current biasing that at least 1 modulating sections of giving in these a plurality of modulating sections applies;
Detect according to changing from the light wave pair light quantity corresponding that applies the modulating sections emission that makes overlapping modulation signal of this low frequency signal or direct current biasing with this low frequency signal;
Change based on the light quantity of this detection, the direct current biasing of whole or a part of modulating sections of these a plurality of modulating sections is controlled.
6, the bias control method of photomodulator according to claim 5 is characterized in that, comprises:
The control of the direct current biasing of whole or a part of modulating sections of these a plurality of modulating sections is for changing decision and the control controlled quentity controlled variable corresponding with each modulating sections based on this light quantity.
7, a kind of bias controller of photomodulator, photomodulator has the substrate of electric optical effect; The optical waveguide that on this substrate, forms; Be used for a plurality of modulating sections that the light wave of propagating at this optical waveguide is modulated; Be arranged on the optical superposition portion that the light wave that is used for that this a plurality of modulating sections is modulated carries out this optical waveguide of ripple stack, be used for the direct current biasing of these a plurality of modulating sections is controlled, it is characterized in that, comprise:
The direct current biasing applying mechanism, it is used for applying direct current biasing to these a plurality of modulating sections;
The low frequency signal superposing circuit, it makes the low frequency signal with characteristic frequency and modulation signal or the direct current biasing overlaid of applying for these a plurality of modulating sections;
Light detecting mechanism, its light quantity to the light wave by this ripple stack portion change and detect; With
The biasing control gear, it extracts the light quantity variation corresponding with this low frequency signal out from this light detecting mechanism, and the light quantity based on this extraction changes simultaneously, and this direct current biasing applying mechanism is controlled.
8, the bias controller of photomodulator according to claim 7 is characterized in that,
This low frequency signal superposing circuit has the low frequency signal generating unit of a plurality of generation low frequency signals corresponding with each modulating sections.
9, the bias controller of photomodulator according to claim 7 is characterized in that,
This low frequency signal superposing circuit has 1 the low frequency signal generating unit that produces low frequency signal, will switch from the low frequency signal of this low frequency signal generating unit to offer each modulating sections.
10, a kind of bias controller of photomodulator, photomodulator has the substrate of electric optical effect; The optical waveguide that on this substrate, forms; Be used for a plurality of modulating sections that the light wave of propagating at this optical waveguide is modulated; Be arranged on the optical superposition portion that the light wave that is used for that this a plurality of modulating sections is modulated carries out this optical waveguide of ripple stack, be used for the direct current biasing of these a plurality of modulating sections is controlled, it is characterized in that, comprise:
The direct current biasing applying mechanism, it is used for applying direct current biasing to these a plurality of modulating sections;
The low frequency signal superposing circuit, modulation signal or direct current biasing overlaid that it applies the low frequency signal with characteristic frequency and at least 1 modulating sections of giving in these a plurality of modulating sections;
Light detecting mechanism, it changes the light quantity corresponding with this low frequency signal and detects by from applying the light wave of the modulating sections emission that makes overlapping modulation signal of this low frequency signal or direct current biasing; With
The biasing control gear, it extracts the light quantity variation corresponding with this low frequency signal out from this light detecting mechanism, and the light quantity based on this extraction changes simultaneously, and the direct current biasing applying mechanism of the whole or a part of modulating sections in these a plurality of modulating sections is controlled.
11, according to the bias controller of each the described photomodulator in the claim 7～10, it is characterized in that,
This light detecting mechanism detects the light wave of radially launching in this substrate from this optical waveguide.
12, according to the bias controller of each the described photomodulator in the claim 7～10, it is characterized in that,
This light detecting mechanism detects the light wave of being derived by near the directional coupler that is configured in this optical waveguide.
13, according to the bias controller of each the described photomodulator in the claim 7～10, it is characterized in that,
This light detecting mechanism adopts the light wave after the dropinsert equipment structure carries out along separate routes to detect to making from the light wave of this photomodulator emission.
14, according to the bias controller of each the described photomodulator in the claim 11～13, it is characterized in that,
This light detecting mechanism, it has the photodetector more than at least 2.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP092777/2003 | 2003-03-28 | ||
| JP2003092777 | 2003-03-28 | ||
| JP334793/2003 | 2003-09-26 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1764864A true CN1764864A (en) | 2006-04-26 |
| CN100373217C CN100373217C (en) | 2008-03-05 |
Family
ID=36748311
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB2004800082646A Expired - Fee Related CN100373217C (en) | 2003-03-28 | 2004-03-26 | Method and device for controlling bias of optical modulator |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN100373217C (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2009021451A1 (en) * | 2007-08-10 | 2009-02-19 | Huawei Technologies Co., Ltd. | Bias control methods and systems for plurality of mz modulators |
| CN103941516A (en) * | 2014-05-06 | 2014-07-23 | 中国科学院半导体研究所 | Adjustable high-frequency impulse light source based on silicon-based micro-ring resonant cavity carrier chromatic dispersion effect |
| CN104699155A (en) * | 2015-02-14 | 2015-06-10 | 深圳帕格精密系统有限公司 | Method and device for digitally and automatically controlling bias voltage of electro-optic light modulator |
| WO2015131843A1 (en) * | 2014-03-07 | 2015-09-11 | Huawei Technologies Co., Ltd. | System and method for chromatic dispersion tolerant direct optical detection |
| CN106324866A (en) * | 2015-06-19 | 2017-01-11 | 中兴通讯股份有限公司 | Bias point control device for silicon-based modulator |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4086912B2 (en) * | 1995-09-11 | 2008-05-14 | 富士通株式会社 | Control device for optical modulator |
| JPH10178418A (en) * | 1996-12-19 | 1998-06-30 | Fujitsu Ltd | Optical time division demultiplexer, demultiplex signal changeover method and optical time division multiplex system |
| JP3723358B2 (en) * | 1998-11-25 | 2005-12-07 | 富士通株式会社 | Optical modulation device and optical modulator control method |
-
2004
- 2004-03-26 CN CNB2004800082646A patent/CN100373217C/en not_active Expired - Fee Related
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2009021451A1 (en) * | 2007-08-10 | 2009-02-19 | Huawei Technologies Co., Ltd. | Bias control methods and systems for plurality of mz modulators |
| WO2015131843A1 (en) * | 2014-03-07 | 2015-09-11 | Huawei Technologies Co., Ltd. | System and method for chromatic dispersion tolerant direct optical detection |
| CN103941516A (en) * | 2014-05-06 | 2014-07-23 | 中国科学院半导体研究所 | Adjustable high-frequency impulse light source based on silicon-based micro-ring resonant cavity carrier chromatic dispersion effect |
| CN103941516B (en) * | 2014-05-06 | 2017-01-18 | 中国科学院半导体研究所 | Adjustable high-frequency impulse light source based on silicon-based micro-ring resonant cavity carrier chromatic dispersion effect |
| CN104699155A (en) * | 2015-02-14 | 2015-06-10 | 深圳帕格精密系统有限公司 | Method and device for digitally and automatically controlling bias voltage of electro-optic light modulator |
| WO2016127800A1 (en) * | 2015-02-14 | 2016-08-18 | 深圳帕格精密系统有限公司 | Method and device for controlling digital automatic bias voltage of electro-optical optical regulator |
| US10158428B2 (en) | 2015-02-14 | 2018-12-18 | Plugtech Precision Systems Limited (Shenzhen) | Method and apparatus for digitally and automatically controlling a bias voltage of electro-optic optical modulator |
| CN106324866A (en) * | 2015-06-19 | 2017-01-11 | 中兴通讯股份有限公司 | Bias point control device for silicon-based modulator |
| CN106324866B (en) * | 2015-06-19 | 2020-01-07 | 中兴通讯股份有限公司 | Silicon-based modulator bias point control device |
Also Published As
| Publication number | Publication date |
|---|---|
| CN100373217C (en) | 2008-03-05 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN1048094C (en) | Optical device | |
| JP5874202B2 (en) | OPTICAL TRANSMITTER, ITS CONTROL METHOD, AND OPTICAL TRANSMISSION SYSTEM | |
| CN1815930A (en) | Optical receiver and optical reception method compatible with differential quadrature phase shift keying | |
| CN1244207C (en) | Method and apparatus for minimizing intensity of specific frequency component of optical signal travelling through optical fiber transmission line to thereby minimize total dispersion | |
| JP5773440B2 (en) | Light modulator | |
| CN1410800A (en) | Light modulator and light modulating method | |
| CN105656563B (en) | Optical transmitter and bias control method for optical modulator | |
| CN105738080B (en) | A kind of optical device measurement of spectral response method and measurement apparatus | |
| JP2004318052A (en) | Method for bias control over optical modulator and device therefor | |
| CN108351541A (en) | The control method of optical transmitter and bias voltage | |
| US20110304900A1 (en) | Acousto-optical system, microscope and method of use of the acousto-optical system | |
| EP2840444A3 (en) | Apparatus and method for controlling an optical modulator | |
| CN1191483C (en) | Light device | |
| JP2008116865A (en) | Nested modulator | |
| JP5077480B2 (en) | Optical waveguide device | |
| CN1764864A (en) | Method and device for controlling bias of optical modulator | |
| CN1457571A (en) | Phase modulator and phase modulating method | |
| JP2012137541A (en) | Modulator, transmitter, and communication system | |
| JP5104802B2 (en) | Light modulator | |
| US20130129361A1 (en) | Optical transmitter module and transmitting method | |
| JP2003315860A (en) | Apparatus and method for optical frequency conversion | |
| CN1568423A (en) | Polarization mode dispersion measuring device, method, recording medium | |
| JP2010217633A (en) | Optical modulator | |
| CN1742207A (en) | Optic fiber current sensor, comprising several sensing heads | |
| CN1525225A (en) | Wavelength conversion device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20080305 Termination date: 20190326 |