CN213210534U

CN213210534U - Small high-performance variable optical attenuator

Info

Publication number: CN213210534U
Application number: CN202021629905.2U
Authority: CN
Inventors: 洪亮; 张笃峰
Original assignee: SHANGHAI CHINA SCIENCE FIBEROPTIC COMPONENTS CO Ltd; Shanghai China Sciences Co ltd; Shanghai Zhongke Chuangxin Communication Equipment Co ltd
Current assignee: SHANGHAI CHINA SCIENCE FIBEROPTIC COMPONENTS CO Ltd; Shanghai China Sciences Co ltd; Shanghai Zhongke Chuangxin Communication Equipment Co ltd
Priority date: 2020-08-07
Filing date: 2020-08-07
Publication date: 2021-05-14
Anticipated expiration: 2030-08-07

Abstract

The utility model discloses a small-size high performance's variable optical attenuator, this attenuator includes the tube socket, the MEMS chip, the tube cap, lens, the optical fiber head, the encapsulation sleeve, be equipped with two pins on the tube socket, be equipped with the commentaries on classics mirror on the MEMS chip, be equipped with input optical fiber and output optical fiber in the optical fiber head respectively, tube socket central authorities are located to the MEMS chip, the commentaries on classics mirror is done directional rotation under the voltage drive of MEMS chip, the positive pole and the negative pole of MEMS chip are connected respectively to two pins, the tube cap nests in the tube socket, tube cap central authorities are located to lens, the optical fiber head passes through rubber coating fixed connection with lens, the encapsulation sleeve nests in the tube cap outer lane, optical. The attenuator overcomes the defects of the traditional variable optical attenuator, optimizes indexes of WDA, PDA and TDA, improves attenuation stability, reduces size of the attenuator, and has commercial value.

Description

Small high-performance variable optical attenuator

Technical Field

The utility model relates to an optical communication technical field especially relates to a small-size high performance's variable optical attenuator.

Background

The Variable Optical Attenuator (VOA) is widely applied to the technical field of optical communication, and the mainstream technical scheme in the industry at present is to drive a reflector to rotate by adopting a micro-electro-mechanical system (MEMS) to form a deviated light beam and realize an attenuation function. Specifically, the MEMS VOA uses a dual fiber collimator to optically couple to a MEMS turning mirror. The MEMS rotating mirror rotates under the action of voltage, and the reflected light spots deviate from the end face of the output optical fiber, so that light attenuation is formed. The scheme has the advantages of low power consumption, low insertion loss and high reliability. But has the disadvantages of certain Wavelength Dependent Attenuation (WDA), Polarization Dependent Attenuation (PDA), Temperature Dependent Attenuation (TDA) and optical power oscillation in the high attenuation working state. Furthermore, the device diameter is limited by the MEMS chip size, typically

The patent document US7295748 uses a dispersion wedge plate to compensate WDA, which increases device complexity, is costly and is not commercially viable. The patent document US20040008967 optimizes WDA by changing the lens angle, but does not describe the basis for optimization, while this approach degrades return loss. There are several WDA optimization schemes in the industry, but other performance criteria such as PDA, TDA, decay stability, device size, etc. are mentioned.

Disclosure of Invention

The utility model aims to solve the technical problem that a small-size high performance variable optical attenuator is provided, the defect of traditional variable optical attenuator device is overcome to this attenuator, optimizes WDA, PDA, TDA index, has improved decay stability, reduces the device size, possesses commercial value.

For solving the technical problem, the utility model discloses small-size high performance variable optical attenuator includes tube socket, MEMS chip, pipe cap, lens, optical fiber head, encapsulation sleeve, be equipped with two pins on the tube socket, be equipped with the commentaries on classics mirror on the MEMS chip, be equipped with input optical fiber and output optical fiber in the optical fiber head respectively, the MEMS chip is located tube socket central authorities, the commentaries on classics mirror is in do directional rotation under the voltage drive of MEMS chip, two pins are connected respectively the positive pole and the negative pole of MEMS chip, the pipe cap nestification in the tube socket, lens are located pipe cap central authorities, the optical fiber head passes through rubber coating fixed connection with lens, the encapsulation sleeve nestification in the pipe cap outer lane, optical fiber head and lens are located in the encapsulation sleeve.

Further, the bottom of the MEMS chip is provided with an insulating substrate and is fixed in the center of the tube seat through insulating glue.

Furthermore, an insulating sealing sleeve is arranged between the two pins and the tube seat.

Further, the tube seat is provided with protruding steps, and the tube cap is nested in the protruding steps of the tube seat.

Further, the encapsulation that the optical fiber head is fixedly connected with the lens is ultraviolet curing glue or heating curing glue.

Further, the lens is a self-focusing lens or a spherical lens, the rotating mirror is located at the front focal point position of the lens, the optical fiber head is located at the rear focal point position of the lens, the lens cylinder is fixed at the opening in the center of the pipe cap through sealing welding, and the lens and the rotating mirror are coaxially arranged.

Further, input optical fibers and output optical fibers in the optical fiber head are arranged along a meridian plane, the front end face of the optical fiber head is an inclined plane, an oblique angle is formed in the meridian plane, the oblique angle is 8 degrees, the rear end face of the lens is an inclined plane, the oblique angle is formed in the meridian plane, the oblique angle is 5-6 degrees, the front end face of the self-focusing lens is a plane, and the front end face of the spherical lens is a spherical surface.

Furthermore, the input optical fiber and the output optical fiber in the optical fiber head are deviated from the axis of the lens by 10-30 μm downwards in the meridian plane.

Furthermore, antireflection films are plated on the front end face of the optical fiber head and the rear end face of the lens.

Furthermore, the input optical fiber is positioned at the high point of the optical fiber head, and the output optical fiber is positioned at the low point of the optical fiber head.

Because the utility model discloses small-size high performance variable optical attenuator has adopted above-mentioned technical scheme, this attenuator includes the tube socket promptly, the MEMS chip, the tube cap, lens, the optical fiber head, the encapsulation sleeve, be equipped with two pins on the tube socket, be equipped with the commentaries on classics mirror on the MEMS chip, be equipped with input optical fiber and output optical fiber in the optical fiber head respectively, tube socket central authorities are located to the MEMS chip, the commentaries on classics mirror is done directional rotation under the voltage drive of MEMS chip, the positive pole and the negative pole of MEMS chip are connected respectively to two pins, the tube cap nests in the tube socket, tube cap central authorities are located to lens, the optical fiber head passes through rubber coating fixed connection with lens, the encapsulation sleeve nests in the tube cap outer. The attenuator overcomes the defects of the traditional variable optical attenuator, optimizes indexes of WDA, PDA and TDA, improves attenuation stability, reduces size of the attenuator, and has commercial value.

Drawings

The invention will be described in further detail with reference to the following drawings and embodiments:

fig. 1 is a schematic structural diagram of a small high-performance variable optical attenuator of the present invention;

FIG. 2 is a schematic view taken along line A-A in FIG. 1;

FIG. 3 is an overall optical path diagram of the present variable optical attenuator;

FIG. 4 is a schematic WDA optical path of the present variable optical attenuator;

FIGS. 5a and 5b are schematic views of reflected light spots at different wavelengths at the end face of a fiber optic head;

FIGS. 6a and 6b are schematic diagrams of two different input settings of the present variable optical attenuator;

FIGS. 7a and 7b are schematic cross-sectional views of the end face of the fiber head in the adjustable optical attenuator;

fig. 8a and 8b are schematic diagrams of two different fiber arrangements in the variable optical attenuator.

Detailed Description

Examples as shown in fig. 1, 2 and 3, the small-sized high-performance variable optical attenuator of the present invention comprises a tube holder 1, a MEMS chip 2, a tube cap 3, a lens 4, an optical fiber head 5, a packaging sleeve 10, two

pins

6 and 7 are arranged on the tube seat 1, a rotating mirror 11 is arranged on the MEMS chip 2, the optical fiber head 5 is internally provided with an input optical fiber 8 and an output optical fiber 9 respectively, the MEMS chip 2 is arranged at the center of the tube seat 1, the rotating mirror 11 is driven by the voltage of the MEMS chip 2 to rotate directionally, the two

pins

6 and 7 are respectively connected with the anode and the cathode of the MEMS chip 2, the tube cap 3 is nested in the tube seat 1, the lens 4 is arranged in the center of the tube cap 3, the optical fiber head 5 is fixedly connected with the lens 4 through an encapsulation 51, the packaging sleeve 10 is nested on the outer ring of the tube cap 3, and the optical fiber head 5 and the lens 4 are positioned in the packaging sleeve 10.

Preferably, the MEMS chip 2 is provided with an insulating substrate 21 at the bottom and fixed at the center of the stem 1 by an insulating adhesive.

Preferably, an insulating sealing sleeve 12 is arranged between the two

pins

6 and 7 and the tube seat 1.

Preferably, the tube base 1 is provided with a protruding step 13, and the tube cap 3 is nested in the protruding step 13 of the tube base 1.

Preferably, the encapsulation 51 fixedly connected with the optical fiber head 5 and the lens 4 is an ultraviolet curing adhesive or a heating curing adhesive.

Preferably, the lens 4 is a self-focusing lens or a spherical lens, the rotating mirror 11 is located at a front focal point position of the lens 4, the fiber head 5 is located at a rear focal point position of the lens 4, the lens 4 cylinder is fixed at the opening in the center of the tube cap 3 by sealing welding, and the lens 4 and the rotating mirror 11 are coaxially arranged.

Preferably, the input optical fiber 8 and the output optical fiber 9 in the optical fiber head 5 are arranged along a meridian plane, the front end face 15 of the optical fiber head 5 is an inclined plane, an oblique angle is arranged in the meridian plane, the oblique angle is 8 degrees, the rear end face 16 of the lens 4 is an inclined plane, the oblique angle is arranged in the meridian plane, the oblique angle is 5-6 degrees, the front end face of the self-focusing lens is a plane, and the front end face of the spherical lens is a spherical surface.

Preferably, the input optical fiber 8 and the output optical fiber 9 in the optical fiber head 5 are deviated from the axis of the lens 4 downwards by 10-30 μm in the meridian plane.

Preferably, the front end face 15 of the optical fiber head 5 and the rear end face 16 of the lens 4 are both plated with antireflection films.

Preferably, the input optical fiber 8 is located at the high point of the optical fiber head 5, and the output optical fiber 9 is located at the low point of the optical fiber head 5 in the optical fiber head 5.

In the variable optical attenuator, the diameter of the protruding step 13 of the tube seat 1 depends on the size of the MEMS chip 2, the diameters of the two

pins

6 and 7, the gap between the pins and the chip and the diameter of the insulating sealing sleeve 12, and the diameter of the protruding step 13 of the tube seat 1 can be realized

The cap 3 may be made of an alloy material such as NiFe 47. The step 13 of the pipe seat 1 is nested in the pipe cap 3, the brim of the pipe cap 3 is slightly turned outwards, and the brim of the pipe cap 3 is the same as the outer edge 14 of the pipe seat 1 in size. The pipe seat 1 and the pipe cap 3 are fixedly sealed by adopting a welding mode. The diameter of the outer edge 14 of the socket 1 depends on the welding process and can be realized

The packaging sleeve 10 may be made of a stainless steel material such as SUS 304. The pipe cap 3 is nested in the packaging sleeve 10, and the brim of the pipe cap 3 is the same as the outer diameter of the packaging sleeve 10. I.e. the diameter of the outer rim 14 of the socket 1 determines the outer diameter of the packaging sleeve 10 and thus the diameter of the device body

The tube cap 3 is provided with a lens 4 which can be a Grin-lens or a C-lens. The lens is set to a forward or backward position such that the turning mirror is located at the front focal point of the lens. The cylinder of the lens 4 is fixed at the central opening of the tube cap 3 by means of sealing welding, so that the lens 4 is coaxial with the rotating mirror 11.

The optical fiber head 5 is fixedly connected with the lens 4 in a rubber coating mode. The glue can be ultraviolet curing glue or heating curing glue. When the environmental temperature changes, the angle of the optical fiber head relative to the lens changes slightly due to the thermal expansion effect of the glue, but the angle change only changes the incident point position of the light on the rotating mirror 11, and does not change the incident angle of the light, so the optical coupling efficiency cannot be changed accordingly. That is, such encapsulation can minimize the temperature dependence of the amount of attenuation. For example, for-40 ℃ to +85 ℃, TDA can be reduced to < + > 1.0dB under the attenuation of 30 dB.

As shown in fig. 3, the optical fiber head comprises an optical fiber head 5, a lens 4 and a rotating mirror 11. The fibre optic head 5 is provided with an input fibre 8 and an output fibre 9. The input optical fibres 8 and the output optical fibres 9 are arranged along a meridian plane. The front end face 15 of the fiber tip 5 is a bevel, the bevel being arranged in the meridian plane. To reduce the echo, the tilt angle is set to 8 °. The rear end face 16 of the lens 4 is also a bevel, also disposed in the meridian plane, but at a different angle to the front end face 15 of the fiber tip. The front facets are shaped differently for different lens types, such as for the Grin-lens, the front facet 17 is planar; for C-lens, the front face 17 is spherical. The rotating mirror 11 is arranged at the front focus of the lens 4, and the optical fiber head 5 is arranged at the rear focus of the lens 4. The input light 81 in the input optical fiber 8 passes through the front end face 15 of the optical fiber head, the rear end face 16 of the lens 4 and the front end face 17 of the lens 4 in sequence, and reaches the reflection point 18 on the rotating mirror 11 through the convergence action of the lens 4. When no voltage is driven, the rotation angle of the rotating mirror 11 is zero. The reflected light 91 passes through the front end face 17 of the lens 4, the rear end face 16 of the lens 4, and the front end face 15 of the optical fiber head 5, and enters the output optical fiber 9.

The refractive index of the optical fiber is about 1.4682, the refractive index of the lens is about 1.5-1.8, and an air gap is arranged between the optical fiber head 5 and the lens 4. To facilitate coaxial packaging, the reflection point 18 must be located at the center of the rotating mirror 11, so the inclination angle of the rear end face 16 of the lens 4 must be set to 5-6 °. In order to make the bisector of the incoming light 81 and the reflected light 91 perpendicular to the turning mirror 11, the fiber tip 5 should be offset downward from the axis of the lens 4 by 10 to 30 μm in the meridian plane.

As shown in fig. 4, when the voltage is applied, the rotating mirror 11 rotates clockwise in the meridian plane. This causes the reflected light 91 to deviate from the core of the output optical fibre 9, producing an optical attenuation of the formula:

wherein, ω is_fIs the mode field radius of the fiber, which is a function of wavelength. The longer the wavelength, omega_fThe larger. dx is the distance of the reflected spot from the core of the output fiber 9, which is also a function of wavelength, since the lens index is wavelength dependent. In fig. 4, the input light 81 is emitted from the front end surface 17 of the lens 4, and the long-wavelength and short-wavelength light beams have an angular difference, which is small and thus not distinguished. The light paths of the reflected light of different wavelengths are distinguished in detail in the figure, wherein the medium wave light path is 91. Since the dispersion relation of the refractive index of the lens 4 is short wavelength maximum and long wavelength minimum, the long wavelength optical path 92 is close to the axis of the lens 4 and correspondingly far away from the core of the output optical fiber 9; the short wave optical path 93 is far from the lens 4 axis and correspondingly close to the core of the output optical fiber 9.

The light paths of the reflected light of different wavelengths can be better illustrated by cross-sectional views. FIG. 5a is a cross-sectional view of the fiber tip end face 15 including the core 90 of the output fiber, the reflected long wave spot 920, and the reflected short wave spot 930. Because the rotating mirror rotates clockwise in the meridian plane, two light spots are above the fiber core. Wherein, the long wave light spot 920 is slightly larger and far away from the fiber core 90, and the short wave light spot 930 is slightly smaller and close to the fiber core 90.

WDA index analysis of the variable optical attenuator is approximately linear in a communication waveband of 1260-1620 nm, namely, WDA indexes can be reflected only by comparing the difference value of attenuation quantities of long waves and short waves. According to the attenuation formula, the difference of the sizes of the short and long wavelength light spots and the difference of the deviation of the core are mutually offset, and WDA is minimized. According to the arrangement, the WDA of the variable optical attenuator under 30dB attenuation is about 8dB in a communication waveband of 1260-1620 nm.

In contrast, if the turning mirror 11 is rotated counterclockwise in the meridian plane, as shown in figure 5b, both spots are under the core. Wherein, the long wave light spot 920 is close to the fiber core 90, and the short wave light spot 930 is far away from the fiber core 90. The difference in the size of the short and long wavelength spots, and the difference in the deviation from the core, are superimposed on each other, and the WDA is maximized. In a communication waveband of 1260-1620 nm, the WDA of the variable optical attenuator under 30dB attenuation is about 12 dB.

The front end face 15 of the optical fiber head 5 and the rear end face 16 of the lens 4 in the variable optical attenuator are both plated with antireflection films, and the level in the industry at present is that the reflectivity is less than 0.2%. Such reflectivity may cause light to oscillate interferometrically between the two interfaces. Such interference oscillations do not degrade the insertion loss and return loss index of the device. However, in the operating state of large attenuation of the variable optical attenuator, power oscillation can be generated, and the stability of large attenuation is affected.

Fig. 6a and 6b show two arrangements, which are identical in that the input fibre 8 is close to the high point of the fibre tip 5 and the output fibre 9 is close to the low point of the fibre tip 5. They differ in that the light input directions are opposite: in fig. 6a, input light 81 is input from the input fiber 8 and reflected light 91 is output from the output fiber 9; in fig. 6b input light 93 is input from the output fiber 9 and reflected light 83 is output from the input fiber 8.

As shown in fig. 6a, when input light 81 reaches rear end face 16 of lens 4, 0.2% of the light energy is converted into reflected light 812 due to the end face reflectivity, and reflected light 812 oscillates and propagates upward in the air gap between end face 15 and end face 16, and does not "leak" into output fiber 9 and affect the power stability of output light 91. Fig. 7a is a schematic cross-sectional view of fig. 6a at the fiber tip end face 15, including the output fiber core 9, the output spot 91, and the reflected spot 812, the reflected spot 812 being remote from the fiber core 9 without overlap. That is, the reflected light 812 does not interfere with the attenuated light output and does not affect power stability.

As shown in fig. 6b, when the input light 93 reaches the rear end face 16 of the lens 4, 0.2% of the light energy is converted into reflected light 932 due to the end face reflectivity, and the reflected light 932 oscillates upwards in the air gap between the end face 15 and the end face 16, with a small portion "leaking" into the input fiber 8.

The core mode field radius of the input fiber 8 is about 5 μm, and since the fiber exit light is divergent, the reflected light 932 spot is amplified in the air gap, the spot is about 64 μm when returning to the end face 15, and about 38 μm off the core of the input fiber 8, and it is calculated that about 10% of the intensity of the reflected light 932 will couple into the core of the input fiber 8, i.e., the intensity of the interference light "leaking" into the input fiber 8 corresponds to 0.2% x 10% to 0.02% (37dB) of the incident light intensity. Fig. 7b is a schematic cross-sectional view of fig. 6b at the fiber tip end face 15, including the input fiber core 8, the output spot 83, and the reflected spot 932, the reflected spot 932 overlapping the fiber core 8. That is, the reflected light 932 may interfere with the attenuated light output, affecting power stability. For example, for a 30dB attenuation, the optical power may fluctuate by about 1 dB.

PDA index analysis of the variable optical attenuator is related to the inclination angle of the interface through which the light propagation path passes, and the larger the interface angle is, the stronger the polarization effect is. On the other hand, for multiple interfaces in the optical path, the overall polarization effect can be cancelled by matching the incident angle direction, thereby reducing the PDA index.

Fig. 8a and 8b show two different arrangements of optical fibres, in which the input optical fibre 8 and the output optical fibre 9 are aligned in the direction of the meridian plane in fig. 8a, and the entrance face of the turning mirror 11 is also in the meridian plane. In figure 8b the input optical fibre 8 and the output optical fibre 9 are arranged perpendicular to the meridian plane, and the entrance face of the turning mirror 11 is also perpendicular to the meridian plane.

In both fig. 8a and fig. 8b, the following discussion applies, and the incident light 81 passes through the fiber head end face 15, the rear end face 16 of the lens 4, and the front end face 17 of the lens 4 in sequence, and is p-polarization-enhanced in the meridian plane direction. Similarly, the reflected light 91 passes through the front end surface 17 of the lens 4, the rear end surface 16 of the lens 4, and the end surface 15 of the fiber head 5 in this order, and is p-polarization-enhanced in the meridian plane direction.

Fig. 8a and 8b are different in that the direction of light incident on the turning mirror 11 is different due to the lens condensing action because the two optical fibers are arranged in different directions.

Specifically, since the incidence plane of the turning mirror 11 in fig. 8a is in the meridian plane, the s-polarization of the reflected light perpendicular to the meridian plane is enhanced. The s-polarization enhancement of the reflection point 18, which counteracts the aforementioned p-polarization enhancement, lowers the device's overall PDA. This reduction is amplified in large attenuation situations, such as PDA reductions <0.2dB for 30dB attenuation, when the turning mirror 11 is rotated under voltage drive. Therefore, this form can effectively lower the PDA.

In contrast, the entrance surface of the turning mirror 11 in fig. 8b is perpendicular to the meridian plane, so the p-polarization of the reflected light in the direction of the meridian plane is enhanced. The p-polarization enhancement of the reflection point 18, which adds to the aforementioned p-polarization enhancement, enhances the PDA as a whole. This enhancement is amplified in large attenuation situations when the turning mirror 11 is rotated under voltage drive, e.g. PDA enhancement to >0.5dB for 30dB attenuation. Therefore, this form would raise the PDA, which is not preferable.

Claims

1. A small high-performance variable optical attenuator is characterized in that: this attenuator includes tube socket, MEMS chip, pipe cap, lens, optical fiber head, encapsulation sleeve, be equipped with two pins on the tube socket, be equipped with the commentaries on classics mirror on the MEMS chip, be equipped with input optical fiber and output optical fiber in the optical fiber head respectively, the MEMS chip is located tube socket central authorities, the commentaries on classics mirror is in make directional rotation under the voltage drive of MEMS chip, two pins are connected respectively the positive pole and the negative pole of MEMS chip, the pipe cap nestification in the tube socket, lens are located pipe cap central authorities, the optical fiber head passes through rubber coating fixed connection with lens, the encapsulation sleeve nestification in the pipe cap outer lane, optical fiber head and lens are located in the encapsulation sleeve.

2. The small high-performance variable optical attenuator of claim 1, wherein: the bottom of the MEMS chip is provided with an insulating substrate and is fixed in the center of the tube seat through insulating glue.

3. The small high-performance variable optical attenuator of claim 1, wherein: and an insulating sealing sleeve is arranged between the two pins and the tube seat.

4. The small high-performance variable optical attenuator of claim 1, wherein: the tube seat is provided with protruding steps, and the tube cap is nested in the protruding steps of the tube seat.

5. The small high-performance variable optical attenuator of claim 1, wherein: the encapsulation that the optical fiber head is fixedly connected with the lens is ultraviolet curing glue or heating curing glue.

6. The small high-performance variable optical attenuator of claim 1, wherein: the lens is a self-focusing lens or a spherical lens, the rotating mirror is located at the front focal point position of the lens, the optical fiber head is located at the rear focal point position of the lens, the cylinder of the lens is fixed at the opening in the center of the pipe cap through sealing welding, and the lens and the rotating mirror are coaxially arranged.

7. The small scale high performance variable optical attenuator of claim 6, wherein: the input optical fiber and the output optical fiber in the optical fiber head are arranged along a meridian plane, the front end face of the optical fiber head is an inclined plane, an oblique angle is arranged in the meridian plane and is 8 degrees, the rear end face of the lens is an inclined plane, the oblique angle is arranged in the meridian plane and is 5-6 degrees, the front end face of the self-focusing lens is a plane, and the front end face of the spherical lens is a spherical surface.

8. The small scale high performance variable optical attenuator of claim 7, wherein: and the input optical fiber and the output optical fiber in the optical fiber head are downwards deviated from the axis of the lens by 10-30 mu m in the meridian plane.

9. The small high-performance variable optical attenuator of claim 1, wherein: and antireflection films are plated on the front end face of the optical fiber head and the rear end face of the lens.

10. The small high-performance variable optical attenuator of claim 1, wherein: the input optical fiber is positioned at the high point of the optical fiber head, and the output optical fiber is positioned at the low point of the optical fiber head.