CN1250997C - Adjustable light attenuator for micro electromechanical system and manufacturing method thereof - Google Patents

Abstract

The present invention discloses an adjustable light attenuator for a micro electromechanical system and a manufacturing method thereof. The adjustable light attenuator comprises a movable light shading element, a first optical fiber and a second optical fiber, wherein the movable light shading element is used for attenuating the energy of a light signal entering the adjustable light attenuator; the first optical fiber is transversely arranged at one side of the movable light shading element, and one end of the first optical fiber facing to the movable light shading element is provided with a first inclined plane; the second optical fiber is transversely arranged at the other side of the movable light shading element, and one end of the second optical fiber facing to the movable light shading element is provided with a second inclined plane; the second optical fiber and the first optical fiber are positioned on the same plane, and the first inclined plane and the second inclined plane are corresponding in parallel and are spaced by first distance; the central axis of the second optical fiber corresponding to the central axis of the first optical fiber offsets by second distance.

Description

MEMS (micro electro mechanical system) adjustable optical attenuator and manufacture method thereof

Technical field

The present invention relates to a kind of adjustable optical attenuator (Variable Optical Attenuator; VOA), relate in particular to a kind of MEMS (micro electro mechanical system) (Micro-Electro-Mechanical Systems with low reflection loss (Return Loss); MEMS) adjustable optical attenuator.

Background technology

Optical attenuator is a kind of device that luminous power is decayed, and is mainly used in occasions such as sensitivity measurement in the fibre system and balance light path power delivery.That general optical attenuator has is in light weight, volume is little, precision is high, good stability, characteristics such as easy to use.At present, along with the maturation of manufacture of semiconductor technology and the progress of micro-electromechanical technology, one MEMS (micro electro mechanical system) adjustable optical attenuator is developed, disclose a kind of adjustable optical attenuator of MEMS (micro electro mechanical system) for 6275320B1 number as United States Patent (USP), its cardinal principle is to utilize actuator (actuator) start in the adjustable optical attenuator chip that one dimmer (shutter) is moved or the different angle that tilts, and blocks light path to change the energy size of output light.

Fig. 1 is the top view of an existing MEMS (micro electro mechanical system) adjustable optical attenuator 10.As shown in Figure 1, two optical fiber 11 and 12 that are arranged in a movable light shield device 13 both sides lay respectively at a fiber orientation device 14 location and are aligned with each other and form a straight line.Thus, movable light shield device 13 can be designed to have the inclined-plane usually, and its purpose is and will reduces via the reflecting part of the emitted light wave (not shown) of the end face 15 of optical fiber 11, to reduce the light wave of reflected back optical fiber 11 inside.Because the light wave of reflection can destroy the phase resonance effect of light wave in the laser resonant cavity, can lower output power of laser and increase noise, influence the function of entire system.Therefore, on the design specification of a MEMS (micro electro mechanical system) adjustable optical attenuator, the reflection loss of inside of optical fibre is preferably less than negative 50 decibels (dB).Yet, be aligned with each other two optical fiber 11 and 12 that form straight line configuration with above-mentioned, because light wave injects to the reflected light that air dielectric can produce a part by optical fiber 11, therefore, light wave can produce reflection at fiber end face 15 places.So the inclined design that only relies on movable light shield device 13 can't be reduced to reflection loss negative 50 decibels in fact effectively, and this reflection loss decibel value that does not reach the specification demand will influence properties of product.

On the other hand, the ultimate principle of optical fiber is to utilize light constantly to form inner full-reflection in optical fiber and allow the very long distance of light wave transmissions, and light reaches minimum in the loss of those ends.Fig. 2 is a synoptic diagram, enters the course of an optical fiber in order to a light to be described.As shown in Figure 2, optical fiber 1 is made up of with coating layer (cladding) 1a dielectric material core layer 1b (core) basically, wherein the refractive index n of core layer 1b ₁Refractive index n than coating layer 1a ₂High slightly, make a light 3 in core layer 1b, cause total reflection.Suppose that light 3 transmits and the critical angle that produces inner full-reflection is θ in optical fiber _c, its ultimate principle is as shown in the formula shown in (1)～(3):

n ₁×sinθ _c＝n ₂×sin?90°＝n ₂ (1)

sinθ _c＝n ₂/n ₁ (2)

θ _c＝sin ^-1(n ₂/n ₁) (3)

In addition, numerical aperture (Numerical Aperture; NA) expression when be optically coupled into optical fiber, can in the fiber optic core layer, cause total reflection the maximum outside incident angle.Maximum outer incident angle when as shown in Figure 2, supposing that light 3 is coupled into optical fiber 1 is θ _A, the light 3 in core layer 1b is θ with central axis 2 angles of optical fiber _B, if air refraction n ₀=1, then

n ₀×sinθ _A＝n ₁×sinθ _B＝n ₁×cosθ _c?(4)

sinθ _A＝n ₁×cosθ _c (5)

$\mathrm{NA}=\sin {\mathrm{\&theta;}}_A=\sqrt{{\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="C0215666800092.png"\; state="\{\{state\}\}">n</figure-callout>}}_1^2-{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="C0215666800092.png"\; state="\{\{state\}\}">n</figure-callout>}}_2^2}---\left(6\right)$

With regard to the optical fiber of a practical application, its core layer refractive index n ₁Be about 1.5, and the coating layer refractive index n ₂Be about 1.485, both gaps are little.Work as n ₂/ n ₁=0.99 o'clock, critical angle θ _cBe about 82 degree, maximum outer incident angle θ _ABe about 12 degree, NA=0.21, in other words, central axis 2 angle theta of light 3 and optical fiber _BBe approximately 8 degree.Therefore, when a light was coupled into optical fiber, its incident angle must be less than 12 degree, and light is when transmitting in optical fiber, light and fiber optic hub axle clamp angle will be limited in could produce inner full-reflection, otherwise light can't transmitting in the core layer of optical fiber in 8 degree.

Therefore, this invention is intended to solve the excessive problem of above-mentioned reflection loss, and can avoid the reflecting part of a light in the core layer of optical fiber, to transmit simultaneously.

Summary of the invention

At the problems referred to above, an object of the present invention is to provide a kind of MEMS (micro electro mechanical system) adjustable optical attenuator that can reduce reflection loss and insertion loss (Insertion Loss).

Another object of the present invention provides a kind of manufacture method of MEMS (micro electro mechanical system) adjustable optical attenuator, can effectively reduce reflection loss and insert loss, thereby make this adjustable optical attenuator meet the specification that fibre system is used.

MEMS (micro electro mechanical system) adjustable optical attenuator of the present invention comprises: a movable light shield element enters the energy of a light signal of this adjustable optical attenuator in order to decay; One first optical fiber is landscape configuration in a side of this movable light shield element, and its end in the face of this movable light shield element has one first inclined-plane; And one second optical fiber, opposite side in this movable light shield element is landscape configuration, its end in the face of this movable light shield element has one second inclined-plane, this second optical fiber and this first optical fiber are in the same plane, this first inclined-plane and this second inclined-plane are parallel relative and at a distance of one first distance, and the central axis of this second optical fiber is offset a second distance with respect to the central axis of this first optical fiber.

In one embodiment, the angle of inclination on this second inclined-plane system is same as the angle of inclination on this first inclined-plane, inserts loss as long as can reduce the reflection and the reduction of this light signal in this first optical fiber.Among one embodiment, this first oblique angle is preferably 8 degree, can effectively reduce reflection ray.

In another embodiment, have a differential seat angle between the angle of inclination on this first inclined-plane and this second inclined-plane, and this differential seat angle falls within the particular range, with reduce this light signal in this first optical fiber reflection and reduce and insert loss.

Be noted that, in above-mentioned each embodiment, the design at the angle of inclination on this first inclined-plane makes this light signal can't produce total reflection at this first inside of optical fibre in the reflecting part at this place, first inclined-plane of this first optical fiber, and this second distance system is decided by the angle of inclination on this first distance and this first inclined-plane.

Therefore, the advantage of MEMS (micro electro mechanical system) adjustable optical attenuator of the present invention is can effectively reflection loss be reduced to below-50 decibels, and then improves the performance of product.

Description of drawings

Fig. 1 is the top view of an existing MEMS (micro electro mechanical system) adjustable optical attenuator;

Fig. 2 is a synoptic diagram, enters the course of an optical fiber in order to a light to be described;

Fig. 3 is the top view of the MEMS (micro electro mechanical system) adjustable optical attenuator of one embodiment of this invention;

Fig. 4 is a synoptic diagram, in order to the course of a light in the key diagram 3 after the reflection of optical fiber angled end-face place; And

Fig. 5 is a synoptic diagram, in order to a light signal in the key diagram 3 by the course behind the optical fiber angled end-face.

[figure number explanation]

1a, 111a～ optical fiber coating 1b, 111b～fiber optic core

2～fiber optic hub axis, 3～light

10,100～adjustable optical attenuator 1,11,12,111,112～optical fiber

13,113～movable light shield device 14,114～fiber orientation device

15,115a, 115b～end face 116,117～light wave

Embodiment

Hereinafter with reference to relevant drawings, MEMS (micro electro mechanical system) adjustable optical attenuator of the present invention is described.

Fig. 3 is the top view of the MEMS (micro electro mechanical system) adjustable optical attenuator of one embodiment of the invention.As shown in Figure 3, MEMS (micro electro mechanical system) adjustable optical attenuator 100 of the present invention is made up of two optical fiber 111,112 and a movable light shield device 113, and wherein, two optical fiber 111 and 112 are to be placed in respectively in the fiber orientation device 114 and to locate.But fiber orientation device 114 of the present invention can be the little groove of a V-shape, a plane positioning groove, a plane positioning projection or by the formed device of the way of other positioning optical waveguides.

Be noted that, first, two fiber orientation devices 114 be made into parallel at grade relatively, laterally be positioned at the both sides of movable light shield device 113 respectively and make end face 115a, the 115b center of two optical fiber 111, the 112 spacing L of being separated by; The second, two fiber orientation devices 114 between a side-play amount S is arranged; And the 3rd, two optical fiber 111 and 112 have an inclined-plane and the angle of inclination is θ in the face of the both ends of the surface 115a of movable light shield device 113 and 115b all are cut into, and end face 115a and 115b are parallel to each other; And the 4th, as shown in Figure 4, end face at optical fiber is cut under the situation on an inclined-plane, the reflecting light 116a that one light wave 116 produces in the angled end-face 115a place of optical fiber, and can't meet the transmission mode of optical fiber, reflecting light 116a can't be at optical fiber 111 inner full-reflections.That is to say that light wave 116a can't transmit in the core layer 111b of optical fiber, therefore can reduce reflection loss effectively.Thus, above-mentioned side-play amount S system designs in response to the existence of oblique angle θ, below will describe the relation of side-play amount S, spacing L and oblique angle θ three in the MEMS (micro electro mechanical system) adjustable optical attenuator of the present invention in detail.

As shown in Figure 5, refraction principle according to light, have under the situation of an oblique angle θ at the end face 115a of optical fiber 111, meeting deviation one angle [alpha] when the light wave 117 in the optical fiber 111 marches to end face 115a place, therefore, must make the end face 115b of the optical fiber 112 that is parallel to optical fiber 111 have identical oblique angle θ and produce a side-play amount S with respect to optical fiber 111, could allow the light wave 117 that penetrates from end face 115a be received by optical fiber 112, in other words, side-play amount S can be along with the size of the oblique angle θ of optical fiber 111 and 112 and is changed.Following formula (7) and (8) the refractive index n of the optical fiber of classifying as 111 core layers ₁, the oblique angle θ of end face 115a, refraction angle α, the air refraction n of light wave 117 ₀, spacing L and side-play amount S relational expression:

n ₁×sinθ＝n ₀×sin(θ+α) (7)

S＝L×tanα (8)

Therefore, reach (8) as can be known from formula (7), at the refractive index n of optical fiber 111 core layers ₁And air refraction n ₀Under the known situation, side-play amount S is real to be determined by spacing L and oblique angle θ.That is we can adjust side-play amount S according to spacing L and oblique angle θ.

In one embodiment of the invention, optical fiber 111 and 112 end face 115a and 115b are cut into the inclined-plane at 8 degree pitch angle, therefore, and core layer (glass material) refractive index n in optical fiber 111 and 112 ₁Be 1.5 and air refraction n ₀Be under 1 the condition, it is 4 degree that the refraction angle α that can calculate light wave 117 according to formula (7) and (8) is close to.It should be noted that when end face when optical fiber is cut into the oblique angle that is approximately 6～12 degree that reflecting light will be dispersed soon and reduce reflection loss.The design of this angled end-face is except allowing the adjustable optical attenuator of MEMS (micro electro mechanical system) of present embodiment meet the specification that optical communication uses, and the reflection loss that has not only improved inside of optical fibre has also reduced and inserted loss.

To sum up, various embodiments of the present invention are described in detail.Yet those of ordinary skills should be appreciated that, each embodiment is described in this and only is the usefulness of illustration, that is, do not breaking away within connotation of the present invention and the scope, this invention is intended to contain the variation example of each item recited above and revise example.Therefore, protection scope of the present invention is defined by appended claim.

Claims (8)

1. a MEMS (micro electro mechanical system) adjustable optical attenuator is characterized in that, comprises:

One movable light shield element is in order to the coupling energy of the light signal of decaying;

One first optical fiber is landscape configuration in a side of this movable light shield element, and its end in the face of this movable light shield element has one first inclined-plane; And

One second optical fiber is landscape configuration in the opposite side of this movable light shield element, and its end in the face of this movable light shield element has one second inclined-plane;

Wherein, this second optical fiber and this first optical fiber are in the same plane, this first inclined-plane is parallel with this second inclined-plane and at a distance of one first distance L, this first distance L is the distance of the projection of center, two inclined-planes on the central axis of optical fiber, and the central axis of this second optical fiber is offset a second distance S with respect to the central axis of this first optical fiber; Described MEMS (micro electro mechanical system) adjustable optical attenuator satisfies following formula:

n ₁×sinθ＝n ₀×sin(θ+α)

S＝L×tanα

In the formula, n ₁Be the refractive index of fiber optic core layer, oblique angle, the n that θ is end face ₀Be that air refraction, α are the refraction angles of light wave.

2. MEMS (micro electro mechanical system) adjustable optical attenuator as claimed in claim 1 is characterized in that: this first inclined-plane is identical with the angle of inclination on this second inclined-plane, inserts loss to reduce the reflection and the reduction of this light signal in this first optical fiber.

3. MEMS (micro electro mechanical system) adjustable optical attenuator as claimed in claim 2 is characterized in that: the design at the angle of inclination on this first inclined-plane makes this light signal can't produce total reflection at this first inside of optical fibre in the reflecting part at this place, first inclined-plane of this first optical fiber.

4. MEMS (micro electro mechanical system) adjustable optical attenuator as claimed in claim 2 is characterized in that: this second distance is decided by this first distance and the angle of inclination on this first inclined-plane.

5. MEMS (micro electro mechanical system) adjustable optical attenuator as claimed in claim 1 is characterized in that: this first optical fiber and this second optical fiber lay respectively in the fiber orientation device.

6. the manufacture method of a MEMS (micro electro mechanical system) adjustable optical attenuator is characterized in that, comprises the following step:

One end face of one first optical fiber is cut into one first inclined-plane;

One end face of one second optical fiber is cut into one second inclined-plane;

In a side of a movable light shield element, this end face that makes this first optical fiber is in the face of this movable light shield element with this first optical fiber landscape configuration; And

Opposite side in this movable light shield element, apart this end face one first distance L place of this first optical fiber is with this second optical fiber landscape configuration, so that this first optical fiber is in the same plane with this second optical fiber and this first inclined-plane is parallel relative with this second inclined-plane, wherein this first distance L is the distance of the projection of center, two inclined-planes on the central axis of optical fiber; And the central axis of this second optical fiber is offset a second distance S with respect to the central axis of this first optical fiber; Described MEMS (micro electro mechanical system) adjustable optical attenuator satisfies following formula:

n ₁×sinθ＝n ₀×sin(θ+α)

S＝L×tanα

In the formula, n ₁Be the refractive index of fiber optic core layer, oblique angle, the n that θ is the inclined-plane ₀Be that air refraction, α are the refraction angles of light wave.

7. the manufacture method of MEMS (micro electro mechanical system) adjustable optical attenuator as claimed in claim 6 is characterized in that: this second distance is decided by this first distance and the angle of inclination on this first inclined-plane.

8. the manufacture method of MEMS (micro electro mechanical system) adjustable optical attenuator as claimed in claim 6 is characterized in that: the design at the angle of inclination on this first inclined-plane makes a light wave can't produce total reflection at this first inside of optical fibre in the reflecting part at this place, first inclined-plane of this first optical fiber.

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