CN202586978U - Analog externally modulated optical transmitter - Google Patents
Analog externally modulated optical transmitter Download PDFInfo
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- CN202586978U CN202586978U CN 201220210406 CN201220210406U CN202586978U CN 202586978 U CN202586978 U CN 202586978U CN 201220210406 CN201220210406 CN 201220210406 CN 201220210406 U CN201220210406 U CN 201220210406U CN 202586978 U CN202586978 U CN 202586978U
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Abstract
The utility model discloses an analog externally modulated optical transmitter, which comprises a secondary distortion control module. Both a first pilot signal generating circuit and a second pilot signal generating circuit of the secondary distortion control module are connected with a hybrid circuit and an intermodulation generator respectively. The intermodulation generator is connected with a synchronous detector. The input end of an optical fiber splitter is connected with the output end of an external modulator. One output end of the optical fiber splitter is connected with the synchronous detector through a detector. The synchronous detector is connected with the direct current bias port of the external modulator through a data processing circuit. The hybrid circuit is connected with the direct current bias port of the external modulator through a primary double T-shaped filter and a high-pass filter. The mixed output of two paths of pilot signals is subjected to the filtering and mixing operation of the primary double T-shaped filter, and then difference-frequency components generated during the above operation are subjected to the filtering operation of the high-pass filter with adjustable output amplitude. Thus, mixed signals beneficial to the control of composite second order (SCO) are filtered out and the control accuracy is improved. The analog externally modulated optical transmitter is adapted to the field of optical fiber communication.
Description
Technical field
The utility model relates to a kind of transmission equipment of CATV fiber optic communication field, especially relates to a kind of 1550nm simulation external modulation optical sender of just bias point being realized stable control.
Background technology
Radiofrequency signal is mainly divided two kinds of direct intensity modulated and external modulation to the modulation technique of optical carrier in optical fiber AM-CATV (amplitude modulation cable TV) transmitter, and directly the intensity modulated technology has been tending towards ripe and in the overwhelming majority's AM-CATV fiber optic transmission system, has used.Though and that the external modulation mode is used for the research of Optical CATV Transmission System is slower, because it possesses many distinct advantages: high like power output, insensitive etc. to the link reflection.Especially setover through reasonable, but intrinsic is eliminated idol time distortion, obtains very high CSO (compound second-order distortion) index.But external modulation just bias point reaches drifts such as ambient temperature in time, thereby can cause the severe exacerbation of CSO.Its control at present is to carry out the method for automatic gain control and carry out concrete the realization as follows through introducing pilot signal mostly: introduce two-way pilot signal ω 1 and ω 2, be divided into two parts after the mixing, a part is directly in the adding modulator biasing circuit; Another part is delivered to the intermodulation component that generation needs in the intermodulation generator.The light signal of modulator output is told a part and is received by detector, after transferring to intermodulation component that the intermodulation generator produces and carrying out synchronous detecting, handles through low pass filter again, obtains an approximate direct current signal and adds in the modulator biasing circuit.Such scheme is directly sent into mixed signal the direct current biasing control circuit of external modulator; Simultaneously directly send into synchronous detector to signal that detector received and the signal that the intermodulation generator is produced, the each harmonic component of their generations can reduce the accuracy that the modulator bias point is controlled; In addition, though synchronous detection is similar to direct current after low pass filter is handled the signal that obtains, alternating component exists still, will the carrier component of CATV be impacted, and finally is unfavorable for the stable control of CSO index.
Summary of the invention
The utility model mainly is to solve the technical problem that the harmonic component that still contains in the mixed signal of existing in prior technology can reduce the accuracy of modulator bias point control, and a kind of simulation external modulation optical sender that can elimination mixes harmonic component in the signal of back, improves the accuracy of bias point control is provided.
The utility model mainly is able to solve through following technical proposals to above-mentioned technical problem: a kind of simulation external modulation optical sender; Comprise that control circuit, first microwave signal source, second microwave signal source, microwave close road module, radio-frequency module, laser control module, second-order distortion (CSO) control module and external modulator; Said control circuit connects first microwave signal source and second microwave signal source respectively; Said first microwave signal source is connected microwave through microwave signal respectively with second microwave signal source and closes the road module; Said external modulator connects microwave respectively and closes road module, radio-frequency module, laser control module and second-order distortion control module; Said second-order distortion control module comprises the first pilot signal generative circuit, the second pilot signal generative circuit, intermodulation generator, synchronizing indicator, data processing circuit, the first double-T shaped filter, high pass filter, hybrid circuit, optical fiber splitter and detector; Said first pilot signal produces circuit and all is connected hybrid circuit and intermodulation generator respectively with second pilot signal generation circuit; Said intermodulation generator is connected with synchronous detector; The input of said optical fiber splitter connects the output of external modulator; An output of said optical fiber splitter is connected with synchronous detector through detector, and said synchronous detector is connected with the direct current biasing mouth of external modulator through data processing circuit, and said hybrid circuit is connected the direct current biasing mouth of external modulator with high pass filter through the first double-T shaped filter.With the difference frequency component of two-way pilot signal error signal as CSO control; For obtaining proportional error signal with CSO; The mixing output of pilot signal is not the dc bias circuit of directly sending into external modulator, but adds the adjustable high pass filter of one-level output amplitude behind the difference frequency component through the double-T shaped filter filtering mixing of one-level back generation again to leach the favourable mixed signal of CSO control.
As preferably, said external modulator is the lithium niobate external modulator.
As preferably, said second-order distortion control module also comprises three grades of low pass filters, linear amplifier circuit and negative circuits, and said intermodulation generator is connected with synchronous detector through three grades of low pass filters, linear amplifier circuit and negative circuits that connect successively.Reliable and stable for the reference signal that is produced by the intermodulation generator that guarantees to send into synchronous detector, the signal that the intermodulation generator is produced is sent into synchronous detector after through the adjustable negative circuit of three grades of LPFs, one-level linear amplifier circuit and one-level amplitude again.
As preferably; Said second-order distortion control module also comprises the second double-T shaped filter, secondary filter circuit and see-saw circuit, and said detector is connected with synchronous detector through the second double-T shaped filter, secondary filter circuit and the see-saw circuit that connects successively.For guaranteeing to send into the accuracy by the error signal that detector received of synchronous detector, send into synchronous detector again after the double-T shaped filter of signal process one-level that detector is received, the filter circuit of secondary band amplitude amplification and the one-level see-saw circuit.
As preferably, said data processing circuit comprises CPU and two subtraction circuits, and a subtraction circuit is connected between CPU and the synchronous detector, and another subtraction circuit is connected between CPU and the external modulator.Because synchronous detection after low pass filter handle the error signal obtain maybe be on the occasion of also being negative value; So earlier this error signal is sent into the subtraction circuit that reference voltage can be regulated; Regulating the reference voltage of subtraction circuit realizes when the error signal of input is 0; Subtraction circuit is output as 1.25V, detects characteristic the most accurately with a half of the reference voltage point that is input as it that makes full use of analog to digital converter, thereby guarantees the accuracy of CSO control indexes to greatest extent.In like manner; The output of digital to analog converter is through similar subtraction circuit; Realize that subtraction circuit is output as 0V, in addition when digital to analog converter is output as 1.25V; Through the resistance in the configuration subtraction circuit, can the scope of subtraction circuit output voltage is consistent with the adjustable range of external modulator direct current biasing point.
For improving the accuracy of modulator bias point control; Reach the stable control of CSO index, this programme all carries out earlier accomplishing synchronous detection again after the processing such as waveform, amplitude and phase place with the two paths of signals of sending into synchronous detector to the mixed signal of sending in the external modulator dc bias circuit.In addition; Synchronous detection is after low pass filter is handled the analog to digital converter that the signal that obtains is sent into CPU earlier; Accomplish the output of digital to analog converter according to the error signal of input by CPU; Again this output is sent in the external modulator direct current biasing control circuit, finally realized the inhibition (be controlled at-65dB below) of the compound second-order distortion index of external modulator (CSO), avoid as much as possible in the direct current biasing control circuit of external modulator, introducing noise signal simultaneously.
The beneficial effect that the utility model brings is; The error signal that obtains after the processing such as mixed signal, reference signal, inter-modulated signal process waveform, amplitude, phase place can reflect the variation of CSO index really; Can measure this error signal through photodetector; System produces control signal corresponding according to its amplitude and adjusts the direct current biasing point; Make the working point of modulator be tending towards the just bias point, when detected error signal near 0 and when remaining unchanged, show that modulator is stabilized on the just bias point.
Description of drawings
Fig. 1 is a kind of structural representation of the utility model;
Fig. 2 is a kind of structural representation of the second-order distortion control module of the utility model;
Among the figure: 1, first microwave signal source, 2, second microwave signal source, 3, microwave closes the road module, 4, control circuit; 5, radio-frequency module, 6, the second-order distortion control module, 7, laser control module, 8, external modulator; 61, the first pilot signal generative circuit, 62, the second pilot signal generative circuit, 63, the intermodulation generator, 64, three grades of low pass filters; 65, linear amplifier circuit, 66, negative circuit, 67, synchronous detector, 68, data processing circuit; 69, hybrid circuit, 70, the first double-T shaped filter, 71, high pass filter, 72, optical fiber splitter; 73, detector, 74, the second double-T shaped filter, 75, the secondary filter circuit, 76, see-saw circuit.
Embodiment
Pass through embodiment below, and combine accompanying drawing, do further bright specifically the technical scheme of the utility model.
Embodiment: a kind of simulation external modulation optical sender of present embodiment; As shown in Figure 1; Comprise that control circuit 4, first microwave signal source 1, second microwave signal source 2, microwave close road module 3, radio-frequency module 5, laser control module 7, second-order distortion (CSO) control module 6 and external modulator 8; Control circuit 4 connects first microwave signal source 1 and second microwave signal source 2 respectively; First microwave signal source 1 is connected microwave through microwave signal respectively with second microwave signal source 2 and closes road module 3, and external modulator 8 connects microwave respectively and closes road module 3, radio-frequency module 5, laser control module 7 and second-order distortion control module 6.
As shown in Figure 2; Second-order distortion control module 6 comprises the double-T shaped filter of the double-T shaped filter of the first pilot signal generative circuit 61, the second pilot signal generative circuit 62, intermodulation generator 63, synchronizing indicator 67, data processing circuit 68, first 70, high pass filter 71, hybrid circuit 69, optical fiber splitter 72, detector 73, three grades of low pass filters 64, linear amplifier circuit 65, negative circuit 66, second 74, secondary filter circuit 75 and see-saw circuit 76; First pilot signal produces circuit 61 and all is connected hybrid circuit 69 and intermodulation generator 63 respectively with second pilot signal generation circuit 62; Intermodulation generator 63 is connected with synchronous detector 67 through three grades of low pass filters 64, linear amplifier circuit 65 and the negative circuit 66 that connects successively; The input of optical fiber splitter 72 connects the output of external modulator 8; An output of optical fiber splitter 72 is connected with synchronous detector 67 with see-saw circuit 76 through the double-T shaped filter of the detector that connects successively 73, second 74, secondary filter circuit 75; Synchronous detector 67 is connected with the direct current biasing mouth of external modulator 8 through data processing circuit 68, and hybrid circuit 69 is connected the direct current biasing mouth of external modulator with high pass filter 71 through the first double-T shaped filter 70.
Data processing circuit 68 comprises CPU and two subtraction circuits, and a subtraction circuit is connected between CPU and the synchronous detector, and another subtraction circuit is connected between CPU and the external modulator.
First microwave signal source is the HMSS-5930 module, and second microwave signal source is the HMSS-1930 module, and it is the HMRF-1959 module that microwave closes the road module, and external modulator is the lithium niobate external modulator.HMSS-5930 module and the adjustable microwave signal of HMSS-1930 module output frequency; And control circuit can be regulated their power output through interface board; Two paths of signals through the HMRF-1959 module close ripple become one the tunnel send into lithium niobate (LiNbO3) external modulator the phase modulation mouth; Control with the optical sender stimulated Brillouin scattering (SBS) of accomplishing present embodiment makes the incident optical power of the fiber amplifier output maximum that is connected with optical sender reach 19dB.Signal amplifies radio frequency (RF) module, veer away into the radio frequency mouth of lithium niobate (LiNbO3) external modulator after the pre-distortion to the 47MHz～862MHz (or 1000MHz, 1080MHz optional) of input, realize the third order distortion index Da Dao of optical sender ≦-65dBc.Second-order distortion (CSO) control module connects the biasing control mouth of lithium niobate (LiNbO3) external modulator; The second-order distortion index Da Dao of realization optical sender ≦-65dBc; The light signal that Distributed Feedback Laser control module power output is reliable and stable, welding is carried out in the optical fiber input port of this flashlight and lithium niobate (LiNbO3) external modulator.Power module is that optical sender provides the Hot Spare power supply.
Specific embodiment described herein only is that the utility model spirit is illustrated.The utility model person of ordinary skill in the field can make various modifications or replenishes or adopt similar mode to substitute described specific embodiment, but can't depart from the spirit of the utility model or surmount the defined scope of appended claims.
Although this paper has used terms such as second-order distortion control, intermodulation generator morely, do not get rid of the possibility of using other term.Using these terms only is in order to describe and explain the essence of the utility model more easily; It all is contrary with the utility model spirit being construed to any additional restriction to them.
Claims (5)
1. simulate the external modulation optical sender for one kind; It is characterized in that; Comprise that control circuit, first microwave signal source, second microwave signal source, microwave close road module, radio-frequency module, laser control module, second-order distortion control module and external modulator; Said control circuit connects first microwave signal source and second microwave signal source respectively; Said first microwave signal source is connected microwave through microwave signal respectively with second microwave signal source and closes the road module; Said external modulator connects microwave respectively and closes road module, radio-frequency module, laser control module and second-order distortion control module; Said second-order distortion control module comprises the first pilot signal generative circuit, the second pilot signal generative circuit, intermodulation generator, synchronizing indicator, data processing circuit, the first double-T shaped filter, high pass filter, hybrid circuit, optical fiber splitter and detector; Said first pilot signal produces circuit and all is connected hybrid circuit and intermodulation generator respectively with second pilot signal generation circuit; Said intermodulation generator is connected with synchronous detector, and the input of said optical fiber splitter connects the output of external modulator, and an output of said optical fiber splitter is connected with synchronous detector through detector; Said synchronous detector is connected with the direct current biasing mouth of external modulator through data processing circuit, and said hybrid circuit is connected the direct current biasing mouth of external modulator with high pass filter through the first double-T shaped filter.
2. simulation external modulation optical sender according to claim 1 is characterized in that said external modulator is the lithium niobate external modulator.
3. simulation external modulation optical sender according to claim 1; It is characterized in that; Said second-order distortion control module also comprises three grades of low pass filters, linear amplifier circuit and negative circuits, and said intermodulation generator is connected with synchronous detector through three grades of low pass filters, linear amplifier circuit and negative circuits that connect successively.
4. according to claim 1 or 2 or 3 described simulation external modulation optical senders; It is characterized in that; Said second-order distortion control module also comprises the second double-T shaped filter, secondary filter circuit and see-saw circuit, and said detector is connected with synchronous detector through the second double-T shaped filter, secondary filter circuit and the see-saw circuit that connects successively.
5. simulation external modulation optical sender according to claim 4; It is characterized in that; Said data processing circuit comprises CPU and two subtraction circuits; A subtraction circuit is connected between CPU and the synchronous detector, and another subtraction circuit is connected between CPU and the external modulator.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201220210406 CN202586978U (en) | 2012-05-11 | 2012-05-11 | Analog externally modulated optical transmitter |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201220210406 CN202586978U (en) | 2012-05-11 | 2012-05-11 | Analog externally modulated optical transmitter |
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| CN202586978U true CN202586978U (en) | 2012-12-05 |
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| CN 201220210406 Expired - Fee Related CN202586978U (en) | 2012-05-11 | 2012-05-11 | Analog externally modulated optical transmitter |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110875780A (en) * | 2018-08-31 | 2020-03-10 | 阿里巴巴集团控股有限公司 | Optical module |
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2012
- 2012-05-11 CN CN 201220210406 patent/CN202586978U/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110875780A (en) * | 2018-08-31 | 2020-03-10 | 阿里巴巴集团控股有限公司 | Optical module |
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| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20121205 Termination date: 20150511 |
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| EXPY | Termination of patent right or utility model |