CN104297850A - Optical attenuator for compensating wavelength dependent loss - Google Patents

Abstract

The invention relates to a variable optical attenuator for optical communication. By adopting an aspheric collimating lens formed by chromatic dispersion optical materials, a reflector driven by a micro-electrical machinery, input and output optical waveguides which are symmetrical to an optical axis of the collimating lens and are inclined, and controlling the rotation direction of the reflector, the variable optical attenuator which is low in cost, low in wavelength dependent loss and low in temperature dependent loss is obtained, so that the requirement of an optical communication system for the optical attenuator is met.

Description

Compensate the optical attenuator of Wavelength Dependent Loss

Technical field

The present invention relates to the optical attenuator of optical communication, particularly relate to a kind of variable optical attenuator with low Wavelength Dependent Loss and low temperature dependent loss.

Background technology

Light signal can be carried out quantitative decay by variable attenuator (hereinafter referred to as optical attenuator), and optical attenuation value can regulate as required, is the important optical device of modern optical communication systems.Based on microelectron-mechanical rotary mirror type optical attenuator, due to its succinct optical design, compact structure and electricity control easily, be widely adopted in Modern optical communication network.In most optical attenuator application scenario, as wavelength-division and dense wavelength division optical-fiber network, in optical fiber, transmission has the light signal of a lot of wavelength, needs to decay to the light signal of all these wavelength simultaneously.

The tiny mirror that microelectron-mechanical rotary mirror type optical attenuator adopts micromechanics to drive, changes the angle of reflection ray, by the effect of collimation lens, is converted into output facula position departing from relative to output waveguide, thus plays the effect of optical attenuation.This optical attenuator has an intrinsic shortcoming, shows as optical attenuation value different with the difference of wavelength, namely usually said Wavelength Dependent Loss (WDL).

It is that wavelength is correlated with that Wavelength Dependent Loss derives from optical waveguide spot size, and for basic mode, wavelength is longer, and the spot size in optical waveguide is larger.Output facula departs from the loss that output optical waveguide causes and is provided by following formula:

$\mathrm{IL}\left(\mathrm{\λ}\right)=4.34\·{\left(\frac{\mathrm{\Δx}}{\mathrm{\ω}\left(\mathrm{\λ}\right)}\right)}^2---\left(1\right)$

Wherein, IL (λ) is insertion loss (i.e. optical attenuation value), and Δ x is the position that output facula departs from output optical waveguide, and ω (λ) is spot size.In a wavelength range, be tied to form vertical just like ShiShimonoseki:

ω(λ)＝a+b·λ (2)

Wherein a and b is dispersion dependent constant.Can see, wavelength is longer, and spot size is larger, and under same bias Δ x, short wavelength will have larger damping capacity relative to long wavelength, produce intrinsic Wavelength Dependent Loss, i.e. WDL.According to (1) formula and (2) formula, can derive Wavelength Dependent Loss WDL is:

$\mathrm{WDL}=-2\·b\·\frac{\mathrm{IL}}{\mathrm{\ω}}\·\mathrm{\Δ\λ}---\left(3\right)$

Can see, along with the increase of pad value IL, Wavelength Dependent Loss WDL also increases thereupon.For the SMF28 optical fiber of conventional Corning Incorporated, in 40 nanometer C-band telecommunication wavelength ranges, b value is about 3.11, and therefore can extrapolate when pad value is 20dB, Wavelength Dependent Loss WDL can reach 1dB, can not meet the requirement of optical communication system.

In existing technical scheme, United States Patent (USP) (US7295748) as shown in Figure 1 have employed a dispersing prism (104) between collimation lens (103) and catoptron (105), to make at light from input waveguide (101) through collimation lens, catoptron, collimation lens, when finally focusing in output waveguide (102), the output facula position of different wave length separates to some extent, and make the relative long wavelength's output facula (108) of short wavelength's output facula (107) closer to output wave guided mode field hot spot (106), in required attenuation range, the Wavelength Dependent Loss produced is contrary with intrinsic WDL symbol, thus greatly reduce the size of Wavelength Dependent Loss.

In existing technical scheme, Chinese patent application (2009100895133) discloses a kind of another scheme compensating Wavelength Dependent Loss, as shown in Figure 2, employ the lens (203) that has dispersion, and the primary optical axis (205) making the position of input waveguide (201) and output optical waveguide (202) depart from lens scarcely with distance (206) and (207), the normal (208) of inclined mirror (204) is coupled to output optical waveguide to make light from input waveguide.As shown in Figure 2 b, this scheme can regard that the collimation lens (212) collimation lens (210) and dispersing prism (211) chromatic dispersion material formed replaces as, add the input and output optical waveguide from axle, thus utilize the dispersion characteristics of lens itself, no longer need a dispersing prism.But the program needs primary optical axis input and output optical waveguide being departed from lens, optical system disalignment, bring very large difficulty to encapsulation.In addition, the encapsulation of out-of-alignment light path also can bring the temperature stability issues of device, in an initial condition, input waveguide (201) and output optical waveguide (202) are symmetrical relative to catoptron normal (208) at the trace (209) of collimation lens opposite side, and both are imaging relations; In temperature changing process, the impact of input waveguide and output optical waveguide expanded by heating departs from original position, its new position---the empty frame (213) in Fig. 2 c and (214), no longer symmetrical at the trace of collimation lens opposite side relative to catoptron normal, emergent ray will depart from output optical waveguide certain distance (215), thus cause the change of insertion loss and optical attenuation value, there is larger temperature correlation loss (TDL).In addition, this application disclose from axle scheme, adopt traditional c-lens and GRIN Lens, off-axis aberration is relatively serious, too increases the insertion loss of device.

Summary of the invention

For the present situation of current optical communication system to optical attenuator demand, the invention provides a kind of low cost, have low Wavelength Dependent Loss, the optical attenuator of low temperature correlation loss, as shown in Figure 3, Fig. 3 a is oblique view, and Fig. 3 b is vertical view, includes:

An input waveguide (301), has first axle (317), the first end face (305) and the first summit (321), for input optical signal;

An output optical waveguide (302), has the second axis (318), the second end face (306) and the second summit (322), for output optical signal;

A collimation lens (303) has a primary optical axis (312), the first focal plane (313) and the second focal plane (314);

A catoptron (304), has normal and a turning axle (323), can rotate around described turning axle.

Input optical signal, through the input of described input waveguide, becomes incident ray, after described collimation lens collimation, incides described catoptron and is reflected, then focus on described output optical waveguide through collimation lens, become emergent ray, and output optical signal.

It is characterized in that:

The normal (307) of the first end face of described input waveguide is tilt relative to the primary optical axis of described collimation lens, there is the first pitch angle (310), when making incident ray incide collimation lens, depart from the primary optical axis of described collimation lens;

The normal (308) of the second end face of described output optical waveguide is tilt relative to the primary optical axis of described collimation lens, has the second pitch angle (311), receives the emergent ray of self-focus lens.

Described collimation lens is made up of dispersing optics material.

Usually, get the first pitch angle and the second pitch angle Tong Jiao, namely equal and opposite in direction, direction are identical, and coordinate with focal plane configuration: the end face of input waveguide and output optical waveguide is placed on first focal plane (313) of collimation lens, catoptron is placed on second focal plane (314) of collimation lens, such incident ray is parallel with emergent ray, and optical system has minimum insertion loss.

Further, input waveguide and output optical waveguide can be made to be placed in same tail optical fiber, be called two optical fiber pigtail.Two naked fibres are normally encapsulated into one by two optical fiber pigtail side by side to be had in the glass capillary of single hole or diplopore and forms, and two optical fiber (optical waveguide) have common end face, when end face have throw angle, have common end slope angle.The central shaft of two optical fiber pigtail can be made further to overlap with the primary optical axis of described collimation lens.

The plane that incident ray (315) forms with the primary optical axis (312) of described collimation lens is called the plane of incidence.In order to obtain maximum dispersion compensation effect, make the line between the first summit of described input waveguide and the second summit of output optical waveguide vertical with the described plane of incidence, the turning axle (323) of described catoptron is got vertical with the described plane of incidence, and makes the normal of catoptron rotate to produce required optical attenuation value to incident ray from the direction of axle.

In order to improve the temperature stability of device, namely obtaining little temperature correlation loss, and having stable optical attenuation value, the first axle of described input waveguide need be parallel with the primary optical axis of collimation lens and symmetrical with the second axis of output optical waveguide; When temperature variation, the input waveguide that thermal expansion causes and output optical waveguide position offset has identical size, direction on the contrary, becomes reflection relation.As at elevated temperatures, input waveguide and output optical waveguide change to reposition---and in Fig. 3 b, empty frame (319) and (312) represent, described reposition is symmetrical about collimation lens primary optical axis and catoptron normal at the trace (324) of collimation lens opposite side, the imaging relations of described input waveguide first summit (321) and output optical waveguide summit (322) is still set up, therefore, this optical system has good temperature stability.

Fig. 4 illustrates and observes in face of incident ray from the primary optical axis direction of collimation lens, the track of the light seen from input waveguide to output optical waveguide.Collimation lens has a transverse axis (407) and a Z-axis (408), and the direction of transverse axis is identical with the line direction on described input waveguide first summit and output optical waveguide second summit.A, E region in Fig. 4 represents the position of input waveguide and output optical waveguide respectively, the position of B region representation light on collimation lens, and C region is light position on the mirror, and D region is the position that emergent ray leaves collimation lens.Because B and D departs from primary optical axis (402), and about the vertical axis of collimation lens, therefore the dispersion interaction of collimation lens in B and D region symbol in horizontal axis is contrary, and in vertical axis, symbol is identical, and net effect is in vertical axis, produce prism effect of dispersion.

Fig. 4 a represents the situation that do not decay, the focal beam spot of emergent ray is near output optical waveguide position E, due to the dispersion interaction of collimation lens, long wavelength's hot spot (403) is separated to some extent with short wavelength's hot spot (404), but owing to substantially overlapping with output optical waveguide position, the Wavelength Dependent Loss showed very little (the WDL first zero that will describe namely); Fig. 4 b indicates decay situation (catoptron rotates rear), and not only long wavelength's hot spot (405) is separated to some extent with short wavelength's hot spot (406), and they also do not overlap with the position E of output optical waveguide, the optical attenuation needed for generation.When reflection mirror rotation shafts is vertical with the plane of incidence, the relative long wavelength's hot spot of short wavelength's hot spot can be made closer to the position E of output optical waveguide, therefore short wavelength has less damping capacity relative to long wavelength, this is contrary from the intrinsic Wavelength Dependent Loss symbol caused because spot size is different, thus reduces WDL.

As previously mentioned, make input waveguide position A and output optical waveguide position E symmetrical relative to the primary optical axis (402) of described collimation lens (401), thermal stability for device is important, when temperature variation, A and E simultaneously away from or near primary optical axis, maintain reflection relation, extra insertion loss can not be introduced, also make pad value more stable.

Described collimation lens needs to be made up of dispersing optics material.Optical material should have less Abbe number (larger dispersion), as Abbe number is less than 60.

Meanwhile, in order to reduce off-axis aberration, adopt non-spherical lens to replace conventional C-lens and GRIN Lens, the focal length of lens can be taken as between 1 to 2mm.

The catoptron adopting microelectron-mechanical to drive can meet the demand of small size and little driving voltage.For the situation that the focal length of lens is 1 to 2mm, the mirror corners needed for 30dB decay is about 0.25 degree, and the diameter of required catoptron is less than 1mm.

Present invention also offers a kind of method of compensating light attenuator Wavelength Dependent Loss, include:

A collimation lens has a primary optical axis, the first focal plane and the second focal plane;

An input waveguide, has first axle and the first end face, is positioned on the first focal plane of described collimation lens.The light signal inputted through described input waveguide is called incident ray, is collimated by incident ray, be called collimated ray with described collimation lens.

A catoptron, has normal and a turning axle, is positioned on the second focal plane of described collimation lens, can rotate around its turning axle, and reflection carrys out the collimated ray of self-focus lens.

Again incided collimation lens by the collimated ray that described catoptron reflects, and be focused, become output light;

An output optical waveguide, has the second axis and the second end face, is positioned on the first focal plane of described collimation lens, accepts the output light from described collimation lens, and output optical signal.

Rotate described catoptron, with described output optical signal of decaying, the anglec of rotation of catoptron is determined by the pad value of required output optical signal.

It is characterized in that:

The normal of the first end face of described input waveguide is tilt relative to the primary optical axis of described collimation lens, has the first pitch angle, departs from the primary optical axis of described collimation lens when making incident ray incide collimation lens;

The normal of the second end face of described output optical waveguide is tilt relative to the primary optical axis of described collimation lens, has the second pitch angle.

Described collimation lens is made up of dispersing optics material.

Make the first described pitch angle and the second pitch angle equal and opposite in direction, direction is identical; Make described input waveguide first axle parallel and symmetrical relative to described collimation lens primary optical axis with output optical waveguide second axis.

The primary optical axis of described incident ray and described collimation lens forms the plane of incidence, makes the turning axle direction of described catoptron vertical with the described plane of incidence.

When input waveguide and output optical waveguide end slope, the effect of dispersion of Fig. 5 collimation lens is coordinated to do to analyze further:

In Fig. 5, α is the pitch angle of input and output optical waveguide (501) end face, and the angle that incident ray becomes with the primary optical axis of collimation lens is β, can push away when end slope angle α is little, have:

β＝(n ₁-1)·α (4)

Wherein n ₁it is the refractive index of input waveguide.Collimation lens (502) has focal distance f, and the effect for incident ray can represent with an equivalent prism (505), and the corner angle of equivalent prism are γ, under certain being similar to, can push away:

$\mathrm{\γ}=\frac{\mathrm{\β}}{(n_2-1)}=\frac{(n_1-1)}{(n_2-1)}\·\mathrm{\α}---\left(5\right)$

N ₂it is the refractive index of collimation lens.Further, the WDL that can be derived from the optical system remnants that Fig. 5 represents is:

$\mathrm{WDL}=4\·\mathrm{IL}\·(-\sqrt{\frac{4.34}{\mathrm{IL}}}\frac{\mathrm{\Δn}}{\mathrm{\Δ\λ}}\mathrm{\γ}\·f-\frac{b}{2})\·\frac{\mathrm{\Δ\λ}}{\mathrm{\ω}}---\left(6\right)$

Wherein, Δ n/ Δ λ is the abbe number of the optical material of composition collimation lens, is negative value in normal dispersion situation.(5) formula is updated to (6) formula obtain:

$\mathrm{WDL}=4\·\mathrm{IL}\·(-\sqrt{\frac{4.34}{\mathrm{IL}}}\frac{\mathrm{\Δn}}{\mathrm{\Δ\λ}}\frac{(n_1-1)}{(n_2-1)}\mathrm{\α}\·f-\frac{b}{2})\·\frac{\mathrm{\Δ\λ}}{\mathrm{\ω}}---\left(7\right)$

(7) typical relation of the WDL expressed by formula and optical attenuation value IL is represented by Fig. 6.Can see from (7) formula, WDL has two zero points, and the first zero is when optical attenuation value IL is zero, i.e. IL=0; Second zero point makes the item in (7) formula bracket be zero, when namely IL takes off train value when IL gets certain value:

$\mathrm{IL}={(-2\sqrt{4.34}\frac{\mathrm{\Δn}}{\mathrm{\Δ\λ}}\frac{(n_1-1)}{(n_2-1)}\frac{\mathrm{\α}\·f}{b})}^2---\left(8\right)$

Fig. 6 a and Fig. 6 b represents the different inclination angle α of corresponding (7) formula, the relation of remaining Wavelength Dependent Loss WDL and optical attenuation value IL, can see that size and the position at second zero point of WDL entirety change with the difference of α---in Fig. 6 a, the second null position is at IL=20dB place, and in Fig. 6 b, the second null position is at IL=16dB place.

Can see, when other parameter is determined, can be distributed, with satisfied different optical communication system to the requirement of WDL by the position at second zero point of size control WDL of control inputs waveguide and output waveguide end slope angle α and remaining WDL.

Accompanying drawing explanation

The existing optical attenuator technology of Fig. 1, adopts dispersing prism to compensate WDL

The existing optical attenuator technology of Fig. 2, adopts dispersion collimation lens and compensates WDL from axle waveguide

Fig. 3 WDL compensating light provided by the invention attenuator

Fig. 4 WDL compensating light provided by the invention attenuator, the trajectory diagram of light

The method that Fig. 5 optical attenuator WDL provided by the invention compensates

Fig. 6 optical attenuator provided by the invention, the WDL curve after compensation

An embodiment of Fig. 7 WDL compensating light provided by the invention attenuator

Embodiment

[embodiment 1]

The optical attenuator embodiment of a compensation Wavelength Dependent Loss provided by the invention, as shown in Fig. 7 a (vertical view) and Fig. 7 b (side view), includes:

An input waveguide optical fiber (701), has first axle (702) and the first summit (716), for input optical signal;

An output waveguide optical fiber (703), has the second axis (704) and the second summit (717), for output optical signal;

A collimation lens (705) has a primary optical axis (706), the first focal plane (707) and the second focal plane (708), is the non-spherical lens of a dispersing optics material composition.

A two optical fiber pigtail (710) has a central axis (711).

The catoptron (709) that a microelectron-mechanical drives, has a turning axle (713), can rotate around described turning axle.

Described input waveguide optical fiber and output waveguide fiber-coaxial symmetric packages are in described two optical fiber pigtails, and the central axis of described pair of optical fiber pigtail overlaps with the primary optical axis of described collimation lens.Input waveguide optical fiber, output waveguide optical fiber and two optical fiber pigtail have a common end face (712), and its normal tilts relative to the primary optical axis of described collimation lens, and pitch angle is expressed as α.

Input optical signal, through the input of described input waveguide optical fiber, becomes incident ray, after described collimation lens collimation, incides described catoptron and is reflected, then focus on described output optical waveguide through collimation lens, become emergent ray, and output optical signal.

The plane that incident ray (715) forms with the primary optical axis (706) of described collimation lens is called the plane of incidence.In order to obtain maximum dispersion compensation effect, make the line between first summit (716) of described input waveguide optical fiber and second summit (717) of output optical waveguide vertical with the described plane of incidence, the turning axle (713) of described catoptron is got vertical with the described plane of incidence, and the direction of the normal of catoptron to incident ray from axle (714) is rotated to produce required optical attenuation value, in this configuration, short wavelength's emergent ray near output waveguide optical fiber, thus will compensate intrinsic Wavelength Dependent Loss WDL relative to long wavelength's emergent ray.

Due to the effect of inclined end face (712), the primary optical axis shape of incident ray and collimation lens at an angle, is expressed as β in figure, makes incident ray depart from described primary optical axis.For obtaining required WDL offset, the relation arranged described by aforementioned (7) formula of inclined angle alpha derives.As a concrete example, if input waveguide optical fiber and output waveguide optical fiber are healthy and free from worry SMF28 optical fiber, the focal length of collimation lens is 1.8mm, the refractive index of collimation lens gets 1.78, Abbe number 41 (k-vc89 as Zhu Tian optical glass company), second zero point of remaining WDL is taken at optical attenuation value 20dB, then required inclined angle alpha is about 14.5 degree.The remaining WDL produced is as shown in earlier figures 6a, and within the scope of 0-20dB optical attenuation, remaining WDL is less than 0.26dB.

In required tilt angle ranges, incident ray is comparatively large from axle relative to collimation lens, and traditional C-lens and the off-axis aberration of gradient-index lens are very large, therefore adopts non-spherical lens to reduce insertion loss.

As previously mentioned, input waveguide optical fiber and output waveguide optical fiber are symmetry relative to collimation lens primary optical axis, also ensure that optical attenuator provided by the invention has low temperature correlation loss.

The value of above-mentioned parameter, just in order to scheme provided by the present invention is described better, is not that the present invention limits.Other valued combinations also can meet requirement of the present invention, without prejudice to spirit of the present invention.

[embodiment 2]

Second embodiment of the present invention is similar to Example 1, end slope angle uniquely unlike described pair of optical fiber pigtail is taken as 13 degree, when optical arrangement and other parameter are identical with embodiment 1, second zero point of the remaining WDL that the present embodiment obtains is at optical attenuation value 16dB place, within the scope of 0-16dB optical attenuation, remaining WDL is less than 0.2dB, as shown in Figure 6 b.

Can see from embodiment 1 with comparing of embodiment 2, the size at the end slope angle of two optical fiber pigtail can be used for controlling the overall size of remaining WDL and the position residing for WDL second zero point.

Claims (17)

1. compensate an optical attenuator for Wavelength Dependent Loss, include:

An input waveguide, has first axle, the first end face and the first summit, for input optical signal;

An output optical waveguide, has the second axis, the second end face and the second summit, for output optical signal;

A collimation lens has a primary optical axis, the first focal plane and the second focal plane;

A catoptron, has normal and a turning axle, can rotate around described turning axle.

Input optical signal, through the input of described input waveguide, becomes incident ray, after described collimation lens collimation, incides described catoptron and is reflected, then focus on described output optical waveguide through collimation lens, become emergent ray, and output optical signal.

It is characterized in that:

The normal of the first end face of described input waveguide is tilt relative to the primary optical axis of described collimation lens, has the first pitch angle, departs from the primary optical axis of described collimation lens when making incident ray incide collimation lens;

The normal of the second end face of described output optical waveguide is tilt relative to the primary optical axis of described collimation lens, has the second pitch angle, receives the emergent ray of self-focus lens.

Described collimation lens is made up of dispersing optics material.

2. a kind of optical attenuator compensating Wavelength Dependent Loss according to claim 1, it is characterized in that, described input waveguide first end face and output optical waveguide second end face are positioned on the first focal plane of described collimation lens, and described catoptron is positioned on the second focal plane of described collimation lens.The first described pitch angle and the second pitch angle equal and opposite in direction, direction is identical.

3. a kind of optical attenuator compensating Wavelength Dependent Loss according to claim 2, is characterized in that, the first described pitch angle and the second pitch angle are between 5 degree to 30 degree.

4. a kind of optical attenuator compensating Wavelength Dependent Loss according to claim 2, is characterized in that, the first summit of described catoptron input waveguide and the second vertex position of output optical waveguide are symmetrical relative to the primary optical axis of described collimation lens.

5. a kind of optical attenuator compensating Wavelength Dependent Loss according to claim 2, the primary optical axis of described incident ray and described collimation lens forms the plane of incidence, it is characterized in that, the turning axle of described catoptron is vertical with the described plane of incidence.

6. a kind of optical attenuator compensating Wavelength Dependent Loss according to claim 5, is characterized in that, the line between the first summit of described input waveguide and the second summit of described output optical waveguide is vertical with the described plane of incidence.

7. a kind of optical attenuator compensating Wavelength Dependent Loss according to claim 5, is characterized in that, described catoptron normal rotates to incident ray from the direction of axle, makes the light decrement needed for emergent ray generation and wavelength dependent loss compensation.

8. a kind of optical attenuator compensating Wavelength Dependent Loss according to claim 2, it is characterized in that, described input waveguide and output optical waveguide are placed in a two optical fiber pigtail, described pair of optical fiber pigtail has central axis, and the first axle of described input waveguide, the second axis of output optical waveguide are also symmetrical relative to the centerline axis parallel of described pair of optical fiber pigtail.

9. a kind of optical attenuator compensating Wavelength Dependent Loss according to claim 8, is characterized in that, the central axis of described pair of optical fiber pigtail overlaps with the primary optical axis of described collimation lens.

10. the optical attenuator of any one the compensation Wavelength Dependent Loss according to claim 1-9, it is characterized in that, described collimation lens is non-spherical lens.

11. any one according to claim 1-9 compensate the optical attenuator of Wavelength Dependent Loss, and it is characterized in that, described catoptron is the catoptron that microelectron-mechanical drives.

The optical attenuator of 12. any one compensation Wavelength Dependent Loss according to claim 10, it is characterized in that, described catoptron is the catoptron that microelectron-mechanical drives.

The method of 13. 1 kinds of compensating light attenuator Wavelength Dependent Losss, includes

A collimation lens has a primary optical axis, the first focal plane and the second focal plane;

An input waveguide, has first axle and the first end face, is positioned on the first focal plane of described collimation lens.The light signal inputted through described input waveguide is called incident ray, is collimated by incident ray, be called collimated ray with described collimation lens.

A catoptron, has normal and a turning axle, is positioned on the second focal plane of described collimation lens, can rotate around its turning axle, and reflection carrys out the collimated ray of self-focus lens.

Again incided collimation lens by the collimated ray that described catoptron reflects, and be focused, become output light;

An output optical waveguide, has the second axis and the second end face, is positioned on the first focal plane of described collimation lens, receives the output light from described collimation lens, and output optical signal.

Rotate described catoptron, with described output optical signal of decaying, the anglec of rotation of catoptron is determined by the pad value of required output optical signal.

It is characterized in that:

The normal of the first end face of described input waveguide is tilt relative to the primary optical axis of described collimation lens, has the first pitch angle, departs from the primary optical axis of described collimation lens when making incident ray incide collimation lens;

The normal of the second end face of described output optical waveguide is tilt relative to the primary optical axis of described collimation lens, has the second pitch angle.

Described collimation lens is made up of dispersing optics material.

The method of 14. a kind of compensating light attenuator Wavelength Dependent Losss according to claim 13, it is characterized in that, make the first described pitch angle and the second pitch angle equal and opposite in direction, direction is identical.

The method of 15. a kind of compensating light attenuator Wavelength Dependent Losss according to claim 14, the primary optical axis of described incident ray and described collimation lens forms the plane of incidence, it is characterized in that, the turning axle direction of described catoptron is vertical with the described plane of incidence.

The method of 16. a kind of compensating light attenuator Wavelength Dependent Losss according to claim 15, is characterized in that, makes described input waveguide first axle parallel and symmetrical relative to described collimation lens primary optical axis with output optical waveguide second axis.

The method of 17. any one compensating light attenuator Wavelength Dependent Loss according to claim 15-16, described output optical signal has two Wavelength Dependent Loss zero points, corresponding to the first pad value and second pad value of described output optical signal, described first pad value is zero, it is characterized in that, determine the size at the first pitch angle of described input waveguide and the second pitch angle of output optical waveguide according to the size of described second pad value.