CN1996074A - Tri-port depolarizing tunable optical filter based on TFF - Google Patents
Tri-port depolarizing tunable optical filter based on TFF Download PDFInfo
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Abstract
The three-port polarizing offset tunable optical filter based on TFF comprises a set or more tunable filter unit with one composed of optical ring connected to the multi channel optical signal input end, a thin film filter, the polarized beam divider A & B on the same light path on the back and forth of the thin film filter plate, featuring in the polarized beam divider A dividing input signal light dividing into P and S parallel lights, with P having half wave plate C rotating P into P-S, two parallel S lights reaching thin film filter plate whose normal line slants on the two parallel S light paths, half wave plate D rotating S into S-P, polarized beam divider B synthesizing P and S into ordinary light signal to output, reflective mirror E paralleling laid with thin film filter plate with reflective mirror F setting behind reflective mirror E with F vertically set with two parallel light paths. It is simple in structure, easy for realization, being able to eliminate polarized relative consumption and polarized light dividing.
Description
Technical field
The present invention relates to a kind of three port adjustable light wave-filters that can eliminate Polarization Dependent Loss and polarized light segregation phenomenon.Specifically, relate to three port adjustable light wave-filters of a kind of based thin film interference filter (TFF) technology.The reconfigurable light path that this three ports adjustable light wave-filter can be widely used in one of Primary Component in the dense wavelength division multiplexing system is multiplexing demultiplexing device ROADM up and down; Thereby also can be applicable to and simplify opto-electronic conversion and monitoring equipment among the optical performance monitor OPM; Can also be with wideband light source in conjunction with constituting tunable optical source; It can also be applied in all many-sides such as sensing network in addition.
Background technology
The technology that can be used for adjustable light wave-filter at present is more, mainly contains F-P chamber type, acousto-optic tunable filter type and optical fiber Bragg light canopy type etc.Wherein, the acousto-optic tunable filter utilization be acoustooptic effect, its tuned speed is fast, but the manufacturing cost height, and its adjacent channel isolation is relatively poor, is not suitable for dwdm system; The utilization of grating type optical fiber adjustable light wave-filter be the optical fiber Bragg diffraction characteristic, the method that adopts the control temperature variation to regulate stress, its bandwidth and adjacent channel isolation are all better, can be used for dwdm system, but its tuning range is little, be subjected to the influence of external environment easily, long-time stability are also good inadequately, in fact all do not realize practical engineering application always; The F-P chamber type adjustable filter utilization in single chamber be the multiple-beam interference effect, the supplier of such in the world two-port tunable optic filter is more now; Domestic units concerned (Shanghai micro-system and the fast scientific ﹠ technical corporation of light) successfully developed sample in 2005 under the support of " 863 " project in early stage, be expected to realize producing in batches and selling in the recent period.But because the transmission curve of this device is a spike, narrow bandwidth, PayLoad signal (the particularly above signal of 10G) there is injury, and its adjacent channel isolation is relatively poor, therefore generally can be used for channel monitoring etc., extract on the road up and down but can not be used for the DWDM signal, also can't constitute the ROADM device.In the dwdm system practical application, the effect of three port adjustable filters is very important.Three port adjustable filters can be when selectivity leaches a certain wavelength light signal, and the continuation that does not influence other non-filter wavelength signals is transmitted forward, and other signals can be via another port output of device.
The technology that is widely used in the fixed wave length multi-cavity interference thin film three port optical filters in the dwdm system at present is quite ripe, has passband wide, the characteristics of isolation height and good stability.This wave filter is that (US4111524 succeeds in developing on basis US4474424) about the invention of GRIN Lens rod and application process thereof in 70 ~ eighties of last century by U.S. Bell laboratory at first.Its structure comprises the film filter of a fixed wave length, a pair of optical fiber collimator that is symmetrical in the film filter placement, and what wherein be connected to the multipath light signal input end is the twin-core fiber collimating apparatus, the other end then is a single-core fiber collimating apparatus.As shown in Figure 1.
Its principle of work is that the light signal of multichannel wavelength is coupled to a twin-core fiber collimating apparatus via optical fiber, after coming out through optical fiber collimator, flashlight is the collimation directional light after a branch of diffusion, shine on the Thin Film Filter of fixed wave length (as λ 1), the light signal of Thin Film Filter transmission λ 1 wavelength is exported through behind single core optical collimator of the other end, and the light signal that will remain wavelength with and the small former twin-core fiber collimating apparatus of angular deviation reflected back, be coupled to another root optical fiber output by it again.The filter wavelength of the filter unit of this scheme is fixed, and does not have adjustability.
Realize aspect the three port adjustable light wave-filters in the characteristic of utilizing this multi-cavity interference thin film DWDM optical filter, two kinds of technology have been developed abroad, one is Japanese SANTEC company, what this technology was used is multi-cavity Thin Film Filter heterogeneous, the film thickness difference that whole optical filter is coated with on diverse location, so the different incoming positions of its incident light on this optical filter, different filtering characteristics is arranged, move this Thin Film Filter with a stepper motor push-and-pull again, to change the incoming position of incident light on optical filter.As shown in Figure 2, this scheme reaches the effect of tunable filtering by stepper motor tuning to optical filter.One big difficult point of this scheme is the preparation of its non-uniform film optical filter, has only one family of Japanese SANTEC company can prepare high-precision like this non-uniform film optical filter at present, and price is very high.Because this scheme requires when the Thin Film Filter upper-lower position moves, any rotation (depth of parallelism＜0.05 degree) can not be arranged up and down in addition, very high to the accuracy requirement of machining, for guaranteeing long-time stability, also very high to the requirement of encapsulation and material.The SANTEC company's market personnel admit, their this adjustable light wave-filter in fact only is suitable as instrument and uses, and uses in telecommunication apparatus, and cost may be too high.In fact on the products catalogue of SANTEC company (http://www.santec.com/products/instruments.htm#OTF-930), this adjustable light wave-filter is classified as meters really.
Another is the patent that is numbered US6943938 that U.S. AFOP company obtained the authorization in 2005, and this scheme utilizes a Thin Film Filter to constitute a filtering device with vertical a placement of completely reflecting mirror.As shown in Figure 3, realize tunable filtering, constituted the tunable optic filter of one three port from face by rotating this filtering device.The problem of this scheme is its folded light beam in filtering by the tuning process of device deflection, certain upper-lower position drift can constantly be arranged, so the optical fiber collimator of reflected light path must move up and down and then.Increase very big difficulty with regard to the reception of giving reflected light signal like this, also just very high to the requirement on machining accuracy of corresponding mechanical parts.
What deserves to be mentioned is that in addition domestic Shandong recruited golden light electronics technology company limited also once to apply for a patent (publication number CN1632633A) in 2003.But this patent is the adjustable filter design of a two-port.As shown in Figure 4, it also is to realize tunable filtering by rotating optical filter.But in design, used birefringece crystal that incident light is resolved into two-way parallel sub light beam quadrature and that spatially separate, use by half-wave plate and Faraday rotator is adjusted into same polarization state with the two-way beamlet again, can realize that so wider tunable filtering has also effectively reduced the Polarization Dependent Loss of device.After the optical filter filtering, reflection and transmission signal through catoptron returns optical filter by original route, birefringece crystal can be merged into the two-way beamlet that returns the single beam of an edge and the different propagated of incident light after the transmission once more, and through lens focus another root optical fiber output to twin-core fiber.The light channel structure more complicated of this scheme, devices such as a large amount of lens that use, half-wave plate, contract type prism, Faraday rotator make that the actual realization of light path is quite complicated, and have increased the loss of device.Its critical defect is that it is the tunable optic filter of a two-port, and after the filtering, other non-filter wavelength light signals all have been scattered, so it is not adapted at the light path practical application of multiplexing demultiplexing device up and down in the dwdm system.
In fact up to the present, also there is not a kind of price lower and can be applied to the three port adjustable light wave-filters of (multiplex/demultiplex) about the signal light path of dwdm system on the whole world optoelectronic device market.
GuangXun Co., Ltd once applied for the patent of three port adjustable filters of a based thin film interference filter technology recently on the basis of above-mentioned these patents, number of patent application 200610019489, and the embodiment of this patent is as shown in Figure 5.What this scheme was used is that the homogeneous film optical filter that improves the pair of parallel placement of film system is realized adjustable light wave-filter.Its principle of work is: the thin-film interference filters that arrives two uniform thickness that keeping parallelism places after the multiplexed light signal in outside is via optical circulator and single-core fiber collimating apparatus (or twin-core fiber collimating apparatus), such two Thin Film Filters have identical filtering characteristic at the light signal incidence point of identical incident angle, the light signal of the identical wavelength of transmissive.The light signal of residue wavelength is through just arriving the completely reflecting mirror of placing perpendicular to reflected light path after the reflection once more.After light signal reflects through completely reflecting mirror, reflected back into the single-core fiber collimating apparatus and the optical circulator of input end successively by two Thin Film Filters, after, so just finished the filtering of one tunnel wavelength light signal by another root optical fiber output by same light path.In the time of need leaching the light signal of another road wavelength, change the angle of inclination of the homogeneous film optical filter of two parallel placements, promptly change the incident angle of light of Thin Film Filter, so just can leach another road light signal.By two parallel Thin Film Filters of synchronous rotation, the angle that constantly changes incident light just can realize the function of adjustable light wave-filter.
Another embodiment of this patent as shown in Figure 6, difference is that input end replaces the combination of input end optical circulator and single-core fiber collimating apparatus with the twin-core fiber collimating apparatus.
This patent is regulated the angle of inclination of two parallel Thin Film Filters by stepper motor, thereby determines the filtering of each road wavelength light signal.Advantage is simple in structure; Use flexibly; Light path is reliable; Film system by design and after improving and optimizating can have bigger tuning range, and its Polarization Dependent Loss is lower; The filtering of twin-stage Thin Film Filter has improved channel isolation or the like.
But also there is a problem in this scheme, though design and optimize film system after the centre wavelength of optical filter two polarized lights the time than wide-angle incident to must be accurate, thereby make Polarization Dependent Loss lower.But along with the increasing of tuning angle, because the variation of two polarized light bandwidth, the polarized light segregation phenomenon can inevitably appear in transmitted light, shown in Fig. 8 (2).This polarized light is separated to the filtering performance that to a certain degree can influence device, has limited the further expansion of tuning range.
Summary of the invention
The objective of the invention is to overcome the shortcoming and defect of above-mentioned prior art, the three port depolarizing tunable optical filters of a kind of based thin film interference filter technology TFF are provided, its filter unit can realize that not only filter wavelength is adjustable, and can eliminate Polarization Dependent Loss and polarized light segregation phenomenon, tuning range can be bigger, and performance is better.Simultaneously owing to the introducing of monitoring Tap/PD and feedback control circuit, to the requirement reduction of mechanical part machining precision.
Technical scheme of the present invention is: based on the three port depolarizing tunable optical filters of TFF, it has one or more groups tunable filter unit, the tunable filter unit of one group, comprise the optical circulator that is connected to the multipath light signal input end, a Thin Film Filter, one is opposite to before and after the Thin Film Filter and polarization beam apparatus A and B on same light path, it is characterized in that: polarization beam apparatus A is separated into P light and the output of S parallel light with input signal light, place half-wave plate C in the P light path P light is rotated to be p-S light, the parallel S light of two-way arrives Thin Film Filter, the normal slope of Thin Film Filter is placed in parallel two-way S light path, half-wave plate D rotates to be s-P light with S light, and polarization beam apparatus B exports after with adjusted P light and the general light signal of S light compositing;
Catoptron F is placed in the parallel placement with Thin Film Filter of catoptron E behind the catoptron E, catoptron F is perpendicular to two parallel light paths.
Aforesaid three port depolarizing tunable optical filters based on TFF is characterized in that: do not have in the Thin Film Filter both sides to place a glass sheet similar to half-wave plate thickness respectively on two light paths of half-wave plate.
Aforesaid three port depolarizing tunable optical filters based on TFF, it is characterized in that: the Tap/PD spectroscopic detectors of placing in the light path behind the polarization beam apparatus B, be electrically connected successively with the driver of digital signal processor DSP chip and stepper motor, Thin Film Filter and catoptron E are fixedly mounted on the stepper motor driven tumbler.
Principle of work of the present invention: when the multiplexed light signal in outside (as 40 tunnel) arrives polarization beam apparatus A via optical circulator, polarization beam apparatus A is separated into parallel output behind P light and the S light with the polarization state of input optical signal, and half-wave plate C is on the light path of P light and with P light and rotates to be S light.After adjusted two-way S light signal arrives the uniform thickness thin-film interference filters that favours the parallel S light signal placement of two-way, Thin Film Filter leaches the two-way S light signal of λ i wavelength, and half-wave plate D rotates to be P light with one road S light signal after the polarization beam apparatus B that is placed by another symmetry exports after closing light.
The parallel S light signal of two-way of the residue of this Thin Film Filter reflection simultaneously wavelength is parallel to the catoptron E of Thin Film Filter placement to another, and remains that the two is parallel.The S light signal of residue wavelength is through just arriving the completely reflecting mirror F that places perpendicular to reflected light path after the reflection once more like this.Two-way S light signal is reflected by Thin Film Filter by same light path through the back of reflection successively of completely reflecting mirror E and F, wherein one road S light is rotated to be P light by half-wave plate C, P light that the two-way reflected in parallel is returned and S light are polarized to be got back to optical circulator and via another root optical fiber output, has so just finished the separation of one tunnel wavelength light signal after beam splitter A closes light.In the time of need leaching the light signal of another road wavelength, change the Thin Film Filter of two parallel placements and the angle of inclination of catoptron E, promptly change the incident angle of light of optical filter, just can leach another road light signal.By the Thin Film Filter and the catoptron E of two parallel placements of synchronous rotation, the angle that constantly changes incident light just can realize the process of tunable filtering.
Because the use of polarization beam apparatus A and B, half-wave plate C and D, what make the tuning transmission of Thin Film Filter is S polarized light in the multipath light signal, so only can not produce Polarization Dependent Loss and phenomenon of polarization to the tuning of a polarization state.And at input and output side, because half-wave plate rotates back to one road S light P light again, so the light signal of each port is not all had influence.What deserves to be mentioned is that being introduced in of half-wave plate can bring certain PMD (polarization dispersion) in the reflected light path, but because the very thin thickness of half-wave plate, less than 0.2mm, so its caused PMD can ignore to the influence of signal of communication.In order to eliminate the PMD that half-wave plate brings, can not have to place the influence that two blocks of glass sheet similar to half-wave plate thickness compensate PMD on two light paths of half-wave plate yet.
The present invention has the following advantages:
1. simple in structure, be easy to realize.By the filtering of next tuning each the road wavelength light signal of stepper motor, use flexibly.The selective light number of channel according to actual needs realizes in the dwdm system tuning range to about 40 road light signals of whole C wave band.What device adopted is uniform film filter, and cost is low.The technology maturation of present multi-cavity DWDM Thin Film Filter, stable performance, the insertion loss is low, so the loss of entire device is also lower.
2. optic path is simple, owing to used completely reflecting mirror to make filtered light signal to turn back to input end according to original route, so just make that two polarization beam apparatus can fixed placement, do not need the process that moves and follow the trail of light signal, make the stable higher of light path, reduced the difficulty of light path debugging, also made to be more prone to realize on the technology.
3. used with the completely reflecting mirror of Thin Film Filter keeping parallelism to have replaced another parallel Thin Film Filter, reduced cost.Because twice of incident light and reflected light so the light signal filtering to single wavelength is more thorough after twice filtering, made channel isolation improve greatly through same Thin Film Filter when reflected light path still can guarantee each filtering.
4. the film system for multi-cavity DWDM Thin Film Filter has carried out improving design and optimization, make it when the incident of incident light angle of inclination, the transmission curve of stablizing and meeting all requirements of DWDM optical filter can be arranged, and its polarized dependent loss PDL and insertion loss are lower, are fit to dynamic tuning in a big way.
5. owing to used polarization beam apparatus and half-wave plate, make that Thin Film Filter only needs to carry out tuning to the S polarized light of mixed light signal, so just thoroughly eliminate Polarization Dependent Loss and improved the small polarized light segregation phenomenon that film system remains, made tuning range increase and improve the tuning performance of device greatly.
6. in order further to improve tuning precision, device has adopted the feedback mechanism of 1%～10% Tap/PD spectroscopic detectors, by the step-wise displacement amount of this spectroscopic detectors, thereby obtain higher tuning precision to the next accurate control step motor of feedback of stepper motor.
In a word, ratio of performance to price height of the present invention uses flexibly, and wide application prospect may be arranged.
Description of drawings
The three port Fixed Wavelength Filters of Fig. 1-Bell Lab.Wherein: 9-twin-core collimating apparatus; 10-Thin Film Filter; 11-single core collimating apparatus.
Fig. 2-Japanese SANTAC company is based on the structural design drawing of three port tunable optic filters of TFF technology.Wherein: 12-twin-core collimating apparatus; 13-contract type non-uniform film optical filter; 14-single core collimating apparatus; 15-stepper motor.
Fig. 3-U.S. AFOP company is based on the structural design drawing of three port tunable optic filters of TFF technology.Wherein: 16,17,18-single core collimating apparatus; 19-Thin Film Filter; 20-completely reflecting mirror; 21-turning axle.
Fig. 4-trick golden light electronics technology company limited is based on the adjustable filter structure side view of the low Polarization Dependent Loss of two-port of TFF technology.Wherein: 22-twin-core fiber; 23-lens; 24,28-birefringece crystal; 25,30-half-wave plate; 26,29-Faraday rotator; 27-contract angle prism; 31-Thin Film Filter; 32-completely reflecting mirror.
Fig. 5-GuangXun Co., Ltd is based on the design proposal 1 of three port tunable optic filters of TFF technology.(patent applied for) wherein: 33-optical circulator; 34,37-single core collimating apparatus; 35,36-Thin Film Filter; 38-completely reflecting mirror.
Fig. 6-GuangXun Co., Ltd is based on the design proposal 2 of three port tunable optic filters of TFF technology.(patent applied for) wherein: 39-twin-core collimating apparatus; 40,41-Thin Film Filter; 42-single core collimating apparatus.
The structural representation of Fig. 7-the present invention's three ports are adjustable filter unit embodiment 1.Wherein: 1-optical circulator; 2-polarization beam apparatus A; 3-half-wave plate C; 4-Thin Film Filter; 5-half-wave plate D; 6-polarization beam apparatus B; 7-catoptron E; 8-catoptron F.
Fig. 8 (1)-improvement film ties up to incident angle 4.3 transmittance graph when spending.Transmission curve is S light, P light and average light (coincidence).
Fig. 8 (2)-improvement film ties up to incident angle 15 transmittance graph when spending.Transmission curve is followed successively by S light, average light and P light from inside to outside.
Fig. 8 (3)-improvement film be behind the depolarization when incident angle 4.8 is spent transmittance graph.Transmission curve is a S light.
Fig. 8 (4)-improvement film be behind the depolarization when incident angle 15 is spent transmittance graph.Transmission curve is a S light.
Fig. 8 (5)-improvement film be behind the depolarization when incident angle 20 is spent transmittance graph.Transmission curve is a S light.
Fig. 9-the present invention's three ports are adjustable filter unit embodiment 2 (comprising the Tap/PD feedback control mechanism).Wherein: 1-optical circulator; 2-polarization beam apparatus A; 3-half-wave plate C; 4-Thin Film Filter; 5-half-wave plate D; 6-polarization beam apparatus B; 7-catoptron E; 8-catoptron F; 43-Tap/PD spectroscopic detectors; 44-DSP control chip; 45-stepper motor driver; 46-step motor control part.
The index comparison sheet of Figure 10-use Tap/PD feedback mechanism and simple Electric Machine Control.
Embodiment
Embodiment 1:
Three port tunable optic filters based on the TFF technology of the present invention have one or more groups tunable filter unit, the structure of the one group is tunable filter unit embodiment as shown in Figure 7, utilize the multi-cavity DWDM Thin Film Filter 4 of a uniform thickness, one is opposite to before and after the Thin Film Filter and the polarization beam apparatus on same light path 2,6, one is opposite to before and after the Thin Film Filter and the half-wave plate on different light paths 3,5, two completely reflecting mirrors 7,8, one of them completely reflecting mirror 7 remains parallel with thin-film interference filters 4 positions, another completely reflecting mirror 8 keeps perpendicular to light path, and an optical circulator 1 constitutes one group of filter unit.
1, principle of work of the present invention is:
After the multiplexed light signal in outside (as 40 tunnel) arrives polarization beam apparatus 2 via optical circulator 1, polarization beam apparatus 2 is separated into parallel output behind P light and the S light with the polarization state of input optical signal, and half-wave plate 3 rotates to be p-S light (the S light that p-S light promptly is rotated into P light by half-wave plate) with P light.After two-way S light signal after tuning arrived the uniform thickness thin-film interference filters 4 that favours the parallel S light signal placement of two-way, Thin Film Filter 4 leached λ
iOne road S light signal is rotated to be s-P light for the two-way S light signal of wavelength, second half wave plate 5 after polarization beam apparatus 6 of being placed by another symmetry closes output (the P light that s-P light promptly is rotated into S light by half-wave plate) behind the light.
The parallel S light signal of two-way of the residue of this Thin Film Filter reflection simultaneously wavelength is parallel to the catoptron 7 of Thin Film Filter 4 placements to another, and remains that the two is parallel.The S light signal of residue wavelength is through just arriving a completely reflecting mirror 8 perpendicular to the reflected light path placement after the reflection once more like this.Two-way S light signal is reflected by Thin Film Filter 4 by same light path through the back of reflection successively of two completely reflecting mirrors, wherein one road S light rotates to be P light after via half-wave plate, the polarization beam apparatus 7 that P light that the two-way reflected in parallel is returned and S light are transfused to end is got back to input end optical circulator 1 and via another root optical fiber output, has so just been finished the filtering of one tunnel wavelength light signal after closing light.In the time of need leaching the light signal of another road wavelength, change the Thin Film Filter of two parallel placements and the angle of inclination of catoptron, promptly change the incident angle of light of Thin Film Filter, so just can leach another road light signal.By Thin Film Filter and the catoptron that rotates two parallel placements, the angle that constantly changes incident light just can realize the tuning filtering process of one three port tunable optic filter.
Each group filter unit can realize that according to the design needs road up and down about about 40 channels selects, and can be implemented in (the tunable filtering process of 40 tunnel single wavelength light signals of 1528nm～1561nm) of whole C wave band in the 100G dwdm system.
2, optical filter design and performance
In the design of our last time of relevant patented claim (application number 200610019489), the multi-cavity DWDM optical filter of use is to design according to satisfying the requirement with certain dynamic tilt incident angle tuning range.Can use two groups of filter units to finish tunable filtering by design to the whole C wavelength band.The tunable wavelength scope of every group of optical filter should be 16 or 17nm, and every group can be satisfied the tuning of 20 channels (100GHz channel spacing).The dynamic-tuning angular range of each group is from 4.8 degree～14.9 degree.In tunable range, the pass band width of its transmission curve is greater than 0.4nm, and cut off band width is less than 1.2nm, and the Polarization Dependent Loss maximal value is less than 0.03dB.Can satisfy the needs of 100GHz dwdm system.
Through after the Design of Depolarization Thin of the present invention, adjustable extent can increase greatly, can reach the tuning range of 33nm, adopts single optical filter just can satisfy the tuning of about 40 channels of whole C wave band (100GHz channel spacing).Its tunable wavelength scope is 1561nm～1528nm.At initial incident angle is 4.8 when spending, and corresponding centre wavelength is 1561nm; When incident angle be tuned to 20 when spending, its centre wavelength moves on to 1528nm.Simulation result is shown in Fig. 8 (5).
3, the depolarized design of device
For the film system that improves after designing, though the big performance of tuning angle is stablized and Polarization Dependent Loss is very low, because P light and S light have the characteristics that P optical transmission rate bandwidth increases and S light transmission bandwidth reduces when oblique incidence.So when angle was big, transmittance graph still existed certain polarized light segregation phenomenon, promptly the transmissivity bandwidth of two polarized lights is inconsistent, and this is unfavorable to further increasing tuning range.Consider that to compare the bandwidth change of S light with original bandwidth less and bandwidth change P light is very big, can obtain bigger and more stable tuning range so only S light is carried out angle tuning.So device has adopted polarization beam apparatus that the S light in the mixed light signal is separated with P light, with half-wave plate P light is rotated to be S light again, Thin Film Filter is only tuning to the S optical signal filtering, can increase tuning range and stability greatly.Utilize half-wave plate and polarization beam apparatus to realize the light that closes of P light and S light again at each output port, realized the phenomenon that device inside elimination Polarization Dependent Loss and polarized light separate.
4, the raising of device tuning precision
Because this device is to use stepper motor that film filter is carried out angle tuning, thereby stepper motor stepping accuracy and repeated very important for the control accuracy of device.Because the requirement to the channel wavelength accuracy of ITU-T regulation of system equipment, if adopt the direct control method of stepper motor, the wavelength control precision that each step of stepper motor can realize will reach 0.03nm at least, this machining accuracy and repeatability to stepper motor itself and mechanical rotation part has proposed very high requirement, has also increased device cost greatly.The stroke of high precision stepper motor is generally all shorter in addition.In embodiments of the invention 2 (referring to Fig. 9), in order to improve the tuning precision of stepper motor, native system has proposed employing Tap/PD feedback mechanism.As shown in Figure 9, solid arrow is a light path part, and dotted arrow is a circuit part.Principle is to use Tap/PD spectroscopic detectors 43 behind transmitted light, tell 1%～10% light signal, carry out automatic peak-seeking by 44 pairs of filtering light of DSP control chip, come stepper motor 45 is fed back, can make stepper motor 45 can adjust the advance and retreat step number automatically, further control the step-wise displacement amount well, therefore improve the stability of tuning precision and system greatly, and reduce requirement and cost the precision of stepper motor own.
Shown in the table of Figure 10, iff simple use high precision stepper motor, its control accuracy need reach 0.03nm, and tuning range is shorter, to the two groups of such filter units of tuning needs and the high precision stepper motor of whole C wave band, cost can increase greatly like this.And after having used the Tap/PD feedback mechanism, it is just much of that accuracy requirement can be reduced to about 0.2nm, after the centre wavelength of Step-Tuned has departed from specified standard centre wavelength, because feedback mechanism can make it to reach requirement by the advance and retreat step number of control core cell adjusting stepper motor.So only one group of filter unit and general stepper motor just can reach the requirement of regulating the whole channels of whole C wave band.
Claims (3)
1, three port depolarizing tunable optical filters based on TFF, it has one or more groups tunable filter unit, the tunable filter unit of one group, comprise the optical circulator that is connected to the multipath light signal input end, a Thin Film Filter, one is opposite to before and after the Thin Film Filter and polarization beam apparatus A and B on same light path, it is characterized in that: polarization beam apparatus A is separated into P light and the output of S parallel light with input signal light, place half-wave plate C in the P light path P light is rotated to be p-S light, the parallel S light of two-way arrives Thin Film Filter, the normal slope of Thin Film Filter is placed in parallel two-way S light path, half-wave plate D rotates to be s-P light with S light, and polarization beam apparatus B exports after with adjusted P light and the general light signal of S light compositing;
Catoptron F is placed in the parallel placement with Thin Film Filter of catoptron E behind the catoptron E, catoptron F is perpendicular to two parallel light paths.
2, three port depolarizing tunable optical filters based on TFF as claimed in claim 1 is characterized in that: do not have in the Thin Film Filter both sides to place a glass sheet similar to half-wave plate thickness respectively on two light paths of half-wave plate.
3, three port depolarizing tunable optical filters based on TFF as claimed in claim 1 or 2, it is characterized in that: the Tap/PD spectroscopic detectors of placing in the light path behind the polarization beam apparatus B, be electrically connected successively with the driver of digital signal processor DSP chip and stepper motor, Thin Film Filter and catoptron E are fixedly mounted on the stepper motor driven tumbler.
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| CNB2006101254956A CN100451703C (en) | 2006-12-18 | 2006-12-18 | Tri-port depolarizing tunable optical filter based on TFF |
| US11/819,530 US7821712B2 (en) | 2006-06-29 | 2007-06-28 | Thin film tunable optical filter |
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| CNB2006101254956A CN100451703C (en) | 2006-12-18 | 2006-12-18 | Tri-port depolarizing tunable optical filter based on TFF |
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| CN100451703C CN100451703C (en) | 2009-01-14 |
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