CN101581836B - Optical interleaver with adjustable high speed isolation and centre wavelength - Google Patents

Abstract

The invention discloses an optical interleaver with adjustable high speed isolation and centre wavelength. A single optical fiber collimator, a first polarization displacement crystal, a first half wave plate group, a first electro light delay plate, a quarter-wave plate, a double refraction crystal, a second half wave plate group, a second electro light delay plate, a third half wave plate group,a second polarization displacement crystal, a fourth half wave plate group, a ridge prism, a third polarization displacement crystal and a double optical fiber collimator are sequentially put in the direction of the same horizontal optical path; parallel beams separated by the second polarization displacement crystal are collimated by the fourth half wave plate group, the ridge prism, the third polarization displacement crystal and coupled to the double optical fiber collimator; the high speed adjustment of the channel separation of the optical interleaver is realized by controlling the firstelectro light delay plate; the high speed adjustment of the centre wavelength of the optical interleaver is realized by controlling the second electro light delay plate. The invention realizes the hi gh speed adjustment of the isolation and the centre wavelength of the optical interleaver, and is characterized by the compact structure, the low cost, the stable performance, etc.

Description

Isolation and centre wavelength high-speed adjustable optical comb filter

Technical field

The present invention relates to fiber optic communication field, relate in particular to a kind of isolation and centre wavelength high-speed adjustable optical comb filter.

Background technology

Increasingly mature along with the develop rapidly of optical fiber communication technology and multimedia communication technology, people are increasing to the demand of data bandwidth.Growing communication flows pressure has been alleviated in the development of dense wave division multipurpose DWDM technology greatly.Optical comb filter is a kind of DWDM device of excellence, except being used for wavelength-division multiplex/demultiplexing, also can be used for the upgrading of power system capacity, for the development of optical-fibre communications provides condition more easily.In addition, optical comb filter can also be applied to aspects such as multiple-wavelength laser, photoeletric measuring system and full optical information processing as a kind of wavelength selective filters efficiently.

Optical comb filter is as a kind of core devices of dwdm system, and people are to its demands for higher performance.At present, the comb filter of using in optical-fibre communications field has several different methods: Sarnia gram (Sagnac) ring, array waveguide grating (AWG) and full optical fiber mach-Ceng De (M-Z) interferometer etc.These comb filter technology can both meet design requirement aspect the key propertys such as insertion loss and isolation preferably.Yet comb filter channel isolation and centre wavelength is non-adjustable, has limited its application in dynamic dwdm system to a great extent.In recent years, constantly the someone proposes the implementation of adjustable comb filter.And, make the response speed of wave filter maintain Millisecond owing to adopt the control method of machinery or liquid crystal electrooptical effect, be difficult to reach the requirement of Modern High-Speed communication network.Based on traditional electrical luminescent crystal lithium columbate crystal LiNO ₃Adjustable filter good response speed is arranged, the right driving voltage of going up kilovolt makes concrete operations become difficult unusually.The application of high-speed adjustable comb filter in dynamic optical communication network is the focus that people pay close attention to always.Comb filter centre wavelength high-speed adjustable makes the action of aspects such as quick adjustment modification of the switching of channel in the dynamic dwdm system and signal simple, effectively.But all the time, our high-speed adjustable of all having ignored the comb filter channel isolation is to influence that optical network system brought.Regulate channel isolation and can implement accurate amplitude control to signal, in conjunction with the dynamic adjustable of centre wavelength, the application in optical communication system will be more extensively and efficiently.Therefore, compare with traditional optical comb filter, the comb filter with isolation and centre wavelength high-speed adjustable can be expanded its development space and application prospect greatly.

Summary of the invention

The objective of the invention is to overcome the deficiency of conventional art, a kind of isolation and centre wavelength high-speed adjustable optical comb filter are provided.

Isolation and centre wavelength high-speed adjustable optical comb filter are: place single fiber collimating apparatus, first polarization displacement crystal, first half wave plate group, the first electric light retardation plate, quarter-wave plate, birefringence delay crystal, second half wave plate group, the second electric light retardation plate, the 3rd half wave plate group, second polarization displacement crystal, the 4th half wave plate group, roof prism, the 3rd polarization displacement crystal and double-fiber collimator on same horizontal optical path direction successively; The parallel beam that is separated by second polarization displacement crystal is coupled to double-fiber collimator through the 4th half wave plate group, roof prism and the 3rd polarization displacement crystal collimation; Realize the high speed adjusting of optical comb filter channel isolation by controlling the first electric light retardation plate; Realize the high speed adjusting of optical comb filter centre wavelength by controlling the second electric light retardation plate; Described first half wave plate group comprises the half-wave plate from the horizontal by 22.5 degree of two symmetrical, second half wave plate group and the 3rd half wave plate group all only comprise the half-wave plate of an optical axis from the horizontal by 22.5 degree, the 4th half wave plate group comprises the half- wave plate 1101 and 1102 of two optical axises from the horizontal by 45 degree, be bonded at the upper left corner and the lower right corner of the right logical light end face of second polarization displacement crystal respectively, the material of the described first electric light retardation plate and the second electric light retardation plate is the transparent ferroelectric ceramics electrooptical material, the material of the described first electric light retardation plate and the second electric light retardation plate is PLZT ceramics or lead magnesio-niobate ceramics, the described first electric light retardation plate and the second electric light retardation plate are rectangular shapes, be coated with metal electrode on its two sides, and on two logical light end faces of retardation plate, be coated with optical anti-reflective film, apply different voltage on two electrodes of electric light retardation plate.

Described birefringence delay crystal is vanadic acid yttrium or rutile crystal.Described birefringence delay crystal is a rectangular shape, and its optical axis is in the plane of logical light end face, and optical axis direction is from the horizontal by miter angle.Described roof prism crestal surface angle and double-fiber collimator form the optically-coupled of mould field coupling.

The present invention is added in the variations in refractive index that the voltage on the electric light retardation plate is regulated the electric light retardation plate by change, and then the phase differential size of the two orthogonal polarized lights of control by the electric light retardation plate, thereby realize the channel isolation in the optical comb filter and the quick dynamic adjustments of centre wavelength.The range of adjustment of centre wavelength can reach whole channel width, and channel isolation can be in maximum isolation degree and 0dB scope accurately regulates arbitrarily, makes the dirigibility of wave filter and adaptability improve greatly.

Adopt transparent ferroelectric ceramics (PLZT ceramics PLZT or lead magnesio-niobate ceramics PMN-PT) as electric light retardation plate material, than traditional LiNbO ₃Crystal has higher light transmission and electrooptical coefficient, lead magnesio-niobate crystal PMN-PT particularly, and its electric light system approximately is LiNbO ₃100 times, thereby make the operating voltage add reduce greatly.And lead magnesio-niobate crystal PMN-PT do not have hesitation clearly, makes the reliability of tunable optical comb filter and degree of accuracy increase.

In addition, can reach submicrosecond level (even reaching for tens nanoseconds) based on the response speed of the tunable optical comb filter of transparent electro-optic ceramics, but the adjusting of quick response system is far superior to other traditional comb filter design proposal.

Description of drawings

Fig. 1 is the structural representation of isolation and centre wavelength high-speed adjustable optical comb filter;

Fig. 2 is four each wave plate and position views that half wave plate group comprises among the present invention;

Fig. 3 is the structural representation of electric light retardation plate among the present invention and birefringence delay crystal;

The transmission spectral line that Fig. 4 changes with the impressed voltage channel isolation for the present invention;

The transmission spectral line of skew takes place in Fig. 5 with impressed voltage centre wavelength for the present invention;

Among the figure: single fiber collimating apparatus 1, first polarization displacement crystal 2, first half wave plate group 3, the first electric light retardation plate 4, quarter-wave plate 5, birefringence delay crystal 6, second half wave plate group 7, the second electric light retardation plate 8, the 3rd half wave plate group 9, second polarization displacement crystal 10, the 4th half wave plate group 11, roof prism 12, the 3rd polarization displacement crystal 13, double-fiber collimator 14.

Embodiment

Further specify the present invention below in conjunction with accompanying drawing:

As shown in Figure 1, isolation and centre wavelength high-speed adjustable optical comb filter are to place single fiber collimating apparatus 1, first polarization displacement crystal 2, first half wave plate group 3, the first electric light retardation plate 4, quarter-wave plate 5, birefringence delay crystal 6, second half wave plate group 7, the second electric light retardation plate 8, the 3rd half wave plate group 9, second polarization displacement crystal 10, the 4th half wave plate group 11, roof prism 12, the 3rd polarization displacement crystal 13 and double-fiber collimator 14 on same horizontal optical path direction successively; The parallel beam that is separated by second polarization displacement crystal is coupled to double-fiber collimator 14 through the 4th half wave plate group 11, roof prism 12 and the 3rd polarization displacement crystal 13 collimations; Realize the high speed adjusting of optical comb filter channel isolation by controlling the first electric light retardation plate 4; Realize the high speed adjusting of optical comb filter centre wavelength by controlling the second electric light retardation plate 8.

Described first polarization displacement crystal 2, second polarization displacement crystal 10 and the 3rd polarization displacement crystal 13 are by vanadic acid yttrium (YVO ₄) wait the material with high birefringence characteristic to make, and on its logical light face, be coated with optical anti-reflective film, strengthen light transmission.A branch of light positive incides this birefringece crystal, is divided into two bundle orthogonal O light in polarization direction and E light, and O light advances along former direction, and deviation and optical axis of crystal directional correlation that E light takes place.

What described first half wave plate group 3, second half wave plate group 7 and the 3rd half wave plate group 9 were comprised all is the half-wave plate of optical axis from the horizontal by 22.5 degree, the 4th half wave plate group 11 is comprised all is the half-wave plates of optical axis from the horizontal by 45 degree, makes the polarization direction of the horizontal direction linearly polarized light by half-wave plate rotate 45 degree and 90 respectively respectively and spends.

In Fig. 1 along the direction of propagation of flashlight to the left from the right side, the position distribution and the optical axis direction of the half-wave plate of first half wave plate group 3, second half wave plate group 7, the 3rd half wave plate group 9 and the 4th half wave plate group 11, as shown in Figure 2.Wherein the first half-wave group 3 comprises the half-wave plate from the horizontal by 22.5 degree of two symmetrical, is bonded at first polarization displacement crystal, 2 right logical light end faces.Second half wave plate group 7 and the 3rd half wave plate group 9 all only comprise the half-wave plates of an optical axis from the horizontal by 22.5 degree, are bonded on the right logical light end faces of birefringence delay crystal 6 respectively and on the logical light face in a left side of second polarization displacement crystal 10.And the 4th half wave plate group 11 comprises the half- wave plate 1101 and 1102 of two optical axises from the horizontal by 45 degree, is bonded at the upper left corner and the lower right corner of second polarization displacement crystal, 10 right logical light end faces respectively.

Described quarter-wave plate 5 is that optical axis parallels with horizontal direction and generation level and orthogonal polarized light differ

Wave plate.In order to make structure compact more, can be bonded at the wave plate of very thin thickness on the logical light end face of birefringece crystal simultaneously.

Described birefringence delay crystal 6 is vanadic acid yttrium (YVO ₄) or rutile (TiO ₂) wait material with high birefringence characteristic.As shown in Figure 3, the birefringence delay crystal is rectangular-shaped, and the distance of its light signal by crystal also is that the length of crystal is d, and optical axis is in the plane of logical light end face, optical axis direction is from the horizontal by miter angle, and is coated with optical anti-reflective film on two logical light end faces.Because birefringence effect, the phase differential of the two orthogonal polarized lights that birefringence delay crystal 6 produces is:

Wherein Δ n is the birefringence rate variance of material, and λ is an optical wavelength.

Described roof prism 12 crestal surface angles and double-fiber collimator 14 form the optically-coupled of mould field coupling, two parallel light beams can be sold off the double-fiber collimator 14 that becomes to have suitable angle outgoing and be coupled to coupling.

The described first electric light retardation plate 4 and the second electric light retardation plate 8 are the transparent ferroelectric ceramics electrooptical materials with high-speed response characteristic and very high electrooptical coefficient.Transparent ferroelectric ceramics is PLZT ceramics (PLZT) or lead magnesio-niobate ceramics (PMN-PT).As shown in Figure 3, the electric light retardation plate is rectangular-shaped, is coated with metal electrode on its two sides, and the distance between two metal electrodes is h, and the also promptly logical electrical distance of the thickness of retardation plate is t, and is coated with optical anti-reflective film on two logical light end faces of retardation plate.Apply different voltage on two electrodes of electric light retardation plate, the refractive index owing to quadratic electro-optical effect (Kerr effect) electric light retardation plate changes under the effect of electric field outside, and two orthogonal polarized lights that pass through will produce the phase differential of a dependence and impressed voltage V:

Wherein R is the electrooptical coefficient of electrooptical material, and n is the refractive index of transparent ferroelectric ceramics during making alive not.The present invention is added in voltage V on the first electric light retardation plate 4 by change ₁Regulate the variations in refractive index of electric light retardation plate 4, and then control is by the phase differential Γ of two orthogonal two polarized lights of electric light phase delay chip 4 ₁Thereby, the Fast Adjustable of realization comb filter channel isolation.The same driving voltage V that regulates on the second electric light retardation plate 8 ₂The phase differential Γ that produces ₂, realize control to comb filter centre wavelength

Described flashlight among Fig. 1 and shone the whole travel path that collimation is coupled into double-fiber collimator 12 from single fiber collimating apparatus 1.Its principle of work is as follows, and the fixed phase difference that birefringence delay crystal 6 produces is δ, and is respectively Γ by the first electric light retardation plate 4 and second electric light time-delay sheet, 8 differing of generation ₁And Γ ₂Utilize the Jones matrix to calculate, and the gain spectrum of trying to achieve comb filter is to whole flashlight communication process:

$T=\frac{1}{2}+\frac{1}{2}\cos {\mathrm{\Γ}}_1\·\sin ({\mathrm{\δ}}_0\left(\mathrm{\λ}\right)+{\mathrm{\Γ}}_2)$

Γ wherein ₁And Γ ₂Be used for regulating the variation of control channel isolation and moving of centre wavelength respectively.

The frequency interval of output spectral line channel can be expressed as:

Wherein c is the light velocity, δ ₀Be differing that the double refraction time delay crystal produces.And the mobile size of filter center frequency with the relational expression that impressed voltage changes is:

$\mathrm{cf}=\frac{\mathrm{\&Gamma;}}{2\mathrm{\&pi;}}\mathrm{\&Delta;f}=\frac{\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="H2009101000741E00011.png"\; state="\{\{state\}\}">c</figure-callout>}}{2\mathrm{\&pi;d}\&CenterDot;\mathrm{\&Delta;n}}\mathrm{\&Gamma;}=\frac{{\mathrm{<figure-callout\; id="3"\; label="tn"\; filenames="H2009101000741E00011.png,H2009101000741E00012.png"\; state="\{\{state\}\}">tn</figure-callout>}}^3\mathrm{RC}}{2\mathrm{\&Delta;n}\&CenterDot;{\mathrm{d\&lambda;h}}^2}{{\mathrm{<figure-callout\; id="2"\; label="V"\; filenames="H2009101000741E00011.png"\; state="\{\{state\}\}">V</figure-callout>}}_2}^2$

And in general the application, can think simply: cf ∝ V ²Can obtain isolation equally from the gain spectrum expression formula is expressed as with the relation of impressed voltage is individual:

$\mathrm{Iso}=\mathrm{<figure-callout\; id="2"\; label="log"\; filenames="H2009101000741E00011.png"\; state="\{\{state\}\}">log</figure-callout>}\frac{2}{1-\cos {\mathrm{\&Gamma;}}_1}=\mathrm{<figure-callout\; id="2"\; label="log"\; filenames="H2009101000741E00011.png"\; state="\{\{state\}\}">log</figure-callout>}\frac{2}{1-\cos \frac{{\mathrm{\&pi;<figure-callout\; id="3"\; label="tn"\; filenames="H2009101000741E00011.png,H2009101000741E00012.png"\; state="\{\{state\}\}">tn</figure-callout>}}^3{{\mathrm{<figure-callout\; id="1"\; label="RV"\; filenames="H2009101000741E00011.png"\; state="\{\{state\}\}">RV</figure-callout>}}_1}^2}{{\mathrm{\&lambda;h}}^2}}({\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="H2009101000741E00011.png"\; state="\{\{state\}\}">V</figure-callout>}}_1>0)$

Work as V ₁=0 o'clock, the channel isolation of comb filter reached maximal value.

The electrooptical effect of transparent ferroelectric ceramics ceramic material has the response speed of submicrosecond.By the voltage that applies of quick adjustment transparent ferroelectric ceramics ceramic material, can realize the high speed dynamic adjustments of the adjustable comb filter submicrosecond of electric light level.

Referring to Fig. 1, flashlight is entered by optical fiber collimator 1 from input optical fibre, through first polarization displacement crystal 2, is divided into the mutually perpendicular line polarisation in two bundle polarization directions, i.e. horizontal polarization light and orthogonal polarized light.Wherein orthogonal polarized light polarization state after first half wave plate group 3 changes, two flashlights of outgoing all become the linearly polarized light that horizontal direction becomes 45 degree, and this has just eliminated the influence to device of polarization mode dispersion (PMD) and Polarization Dependent Loss (PDL) to a great extent.

Through the first electric light retardation plate 4, level and orthogonal polarized light differ generation from Γ ₁, and differing of considering that subsequently quarter-wave plate 5 introduces

Consequently always differ

Control is to the adjusting of isolation.When flashlight during, will produce δ by birefringence delay crystal 4 ₀Fixed skew.Analysis by the front is known, δ ₀Determined that the cycle size of output spectral line is channel frequency separation Δ f.

Flashlight is through second half wave plate group 7, and common rotation 45 degree of the plane of polarization of the polarisation of two-route wire up and down of logical light face differ Γ by 8, the two orthogonal polarized lights generations of electric light retardation plate ₂, Γ ₂Value is brought into play tremendous influence to the phase change of spectral line, and finally causes the mobile variation of centre wavelength (frequency).The 3rd half wave plate group 9 makes linearly polarized light opposite spin 45 degree once more.Incide the two-beam up and down of second polarization displacement crystal 10 this moment, interfere respectively through polarization beam splitting and horizontal polarization light and orthogonal polarized light.Become the four bunch polarisations that polarization state equates left and right sides mutually orthogonal up and down during from 8 outgoing of second polarization displacement crystal, and the light intensity spectral line of four flashlights on this moment horizontal direction is complementary about identical up and down.

Through the 4th half wave plate group 11, the signal polarization state of light obtains adjusting, and makes that the top of inciding the 3rd polarization displacement crystal 13 logical light end faces is horizontal polarization light, and the bottom is an orthogonal polarized light.After the 3rd polarization displacement crystal 13 close bundle, be coupled into double-fiber collimator 14.The polarization state of 12 pairs of light paths of roof prism changes and does not produce any influence, and its adding makes two parallel beams sell off to become to have suitable angle outgoing and be coupled to the double-fiber collimator 14 that is complementary with it.

As shown in Figure 4, on electric light phase delay chip 4, do not apply voltage V ₁The time, the channel isolation of optical comb filter spectral line changes.Figure 5 shows that and apply voltage V ₂The time, the transmission spectral line of optical comb filter is with impressed voltage V ₂Variation and the center is moved.

Claims (4)

1. isolation and centre wavelength high-speed adjustable optical comb filter is characterized in that: place single fiber collimating apparatus (1) successively on same horizontal optical path direction, first polarization displacement crystal (2), first half wave plate group (3), the first electric light retardation plate (4), quarter-wave plate (5), birefringence delay crystal (6), second half wave plate group (7), the second electric light retardation plate (8), the 3rd half wave plate group (9), second polarization displacement crystal (10), the 4th half wave plate group (11), roof prism (12), the 3rd polarization displacement crystal (13) and double-fiber collimator (14); The parallel beam that is separated by second polarization displacement crystal (10) is coupled to double-fiber collimator (14) through the 4th half wave plate group (11), roof prism (12) and the 3rd polarization displacement crystal (13) collimation; Realize the high speed adjusting of optical comb filter channel isolation by controlling the first electric light retardation plate (4); Realize the high speed adjusting of optical comb filter centre wavelength by controlling the second electric light retardation plate (8); Described first half wave plate group (3) comprises the half-wave plate from the horizontal by 22.5 degree of two symmetrical, second half wave plate group (7) and the 3rd half wave plate group (9) all only comprise the half-wave plate of an optical axis from the horizontal by 22.5 degree, the 4th half wave plate group (11) comprises the half-wave plate 1101 and 1102 of two optical axises from the horizontal by 45 degree, be bonded at the upper left corner and the lower right corner of the right logical light end face of second polarization displacement crystal (10) respectively, the material of the described first electric light retardation plate (4) and the second electric light retardation plate (8) is the transparent ferroelectric ceramics electrooptical material, the material of the described first electric light retardation plate (4) and the second electric light retardation plate (8) is PLZT ceramics or lead magnesio-niobate ceramics, the described first electric light retardation plate (4) and the second electric light retardation plate (8) are rectangular shapes, be coated with metal electrode on its two sides, and on two logical light end faces of retardation plate, be coated with optical anti-reflective film, apply different voltage on two electrodes of electric light retardation plate.

2. a kind of isolation according to claim 1 and centre wavelength high-speed adjustable optical comb filter is characterized in that: described birefringence delay crystal (6) is vanadic acid yttrium or rutile crystal.

3. a kind of isolation according to claim 1 and centre wavelength high-speed adjustable optical comb filter, it is characterized in that: described birefringence delay crystal (6) is a rectangular shape, its optical axis is in the plane of logical light end face, and optical axis direction is from the horizontal by miter angle.

4. a kind of isolation according to claim 1 and centre wavelength high-speed adjustable optical comb filter is characterized in that: described roof prism (12) crestal surface angle and double-fiber collimator (14) form the optically-coupled of mould field coupling.

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