CN213210538U - High performance optical coupler - Google Patents
High performance optical coupler Download PDFInfo
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- CN213210538U CN213210538U CN202021628795.8U CN202021628795U CN213210538U CN 213210538 U CN213210538 U CN 213210538U CN 202021628795 U CN202021628795 U CN 202021628795U CN 213210538 U CN213210538 U CN 213210538U
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Abstract
The utility model discloses a high performance optical coupler, this optical coupler includes first optical fiber head, first lens, first glass pipe, the second lens, the second glass pipe, the third glass pipe, beam splitting filter and second optical fiber head, be equipped with input optic fibre and reflection end optic fibre in the first optical fiber head, be equipped with transmission end optic fibre in the second optical fiber head, first lens nestification is managed in first glass, second lens nestification is managed in the second glass, first glass manages and second glass manages nestification and manages in the third glass, first lens and the coaxial arrangement of second lens, the beam splitting filter hugs closely the preceding terminal surface of locating the second lens, first optical fiber head aligns with first lens, the rear end face of second lens is located to the second optical fiber head. The optical coupler overcomes the defects of the traditional fused biconical taper optical coupler, has good flatness, is insensitive to temperature and polarization change, meets the typical indexes of a high-performance optical coupler, and is suitable for high-precision application occasions.
Description
Technical Field
The utility model relates to an optical communication technical field especially relates to a high performance optical coupler.
Background
At present, the optical coupler in the mainstream in the industry adopts a fused tapering technology, that is, two (or more) optical fibers with coating layers removed are closed by a certain method, fused under high-temperature heating and simultaneously stretched towards two sides, finally a special waveguide structure in a biconical form is formed in a heating zone, and different splitting ratios can be obtained by controlling the twisting angle and the stretching length of the optical fibers. Due to the characteristics of the process, the spectrum has larger flatness (Ripple), and the splitting ratio has stronger Temperature Dependence (TDL) and Polarization Dependence (PDL). Especially for the non-uniform coupler, the index of the small splitting ratio port is more degraded. Typical indexes of the fused biconical taper optical coupler are as follows: ripple <0.1dB, TDL <0.2dB, PDL <0.1 dB.
The optical coupler with the index cannot meet the application occasions with high precision, such as laser built-in monitoring. For example, for a laser with 100mW output, an 2/98 non-uniform coupler with 2% of the port with small split ratio as the monitor feedback and 98% of the port with large split ratio as the power output is used. Ideally, the optical power read by the monitoring terminal (P1) is 2mW, the optical power read by the output terminal (P2) is 98mW, and the system compensates for the stability of P2 by monitoring the change of P1. Assuming this non-uniform coupler PDL is 0.2dB, the minimum possible value of P1 is 1.9mW, and the maximum possible value of P2 is 105 mW. To be worse, the system determines that the power is low according to P1, so that the internal circuit is adjusted to make P1 2mW, and P2 becomes 110mW, which causes a large deviation of the laser output value from the expected value. At the same time, larger Ripple and TDL also form similar deviation mechanisms, resulting in unstable laser output power.
For high precision applications, a high performance optical coupler is needed, with typical specifications: ripple <0.05dB, TDL <0.05dB, PDL <0.01 dB.
Disclosure of Invention
The utility model aims to solve the technical problem that a high performance optical coupler is provided, traditional melting of this optical coupler is overcome and is drawn the defect of awl optical coupler, and its flatness is good, and is insensitive to temperature and polarization change, satisfies high performance optical coupler's typical index, is applicable to the application occasion of high accuracy.
In order to solve the technical problem, the utility model discloses high performance optical coupler includes first optical fiber head, first lens, first glass pipe, second lens, second glass pipe, third glass pipe, beam splitting filter and second optical fiber head, be equipped with input optic fibre and reflection end optic fibre in the first optical fiber head, be equipped with transmission end optic fibre in the second optical fiber head, first lens nested in the first glass manages, second lens nested in the second glass manages, first glass pipe and second glass pipe are nested in the third glass manages, first lens and the coaxial arrangement of second lens, beam splitting filter hugs closely and locates the preceding terminal surface of second lens, first optical fiber head with first lens are aimed at, the second optical fiber head is located the rear end face of second lens.
Further, the end face of the first optical fiber head is an inclined plane, the inclination angle of the inclined plane is 8 degrees, an inclined plane meridian is defined as a connecting line between an inclined plane high point and an inclined plane low point along the y direction, the input end optical fiber and the reflection end optical fiber are arranged along the meridian direction, the input end optical fiber faces the inclined plane low point, and the rear end face of the first lens is matched with the end face of the first optical fiber head.
Further, the inclination angle of the inclined plane of the first optical fiber head and the inclination angle of the rear end face of the first lens satisfy (n)f-1)α≈(nc-1) β, where α is the slope angle of the first fiber tip, β is the slope angle of the rear facet of the first lens, nfFor folding the core of an optical fibreRefractive index, ncIs the first lens refractive index.
Further, the end face of the second optical fiber head is an inclined plane, the inclination angle of the inclined plane is 8 degrees, an inclined plane meridian is defined along the x direction, the transmission end optical fiber is located in the center of the inclined plane, and the inclined plane meridian of the first optical fiber head is orthogonal to the inclined plane meridian of the second optical fiber head.
Further, the end face of the beam splitting filter adjacent to the first lens is plated with an antireflection film, the other end face of the beam splitting filter is plated with a beam splitting film, a wedge angle is arranged between the two film-plated end faces of the beam splitting filter, and the wedge angle is 0.7 degrees.
Furthermore, the front end face of the first lens is a spherical surface, the input light and the reflected light passing through the spherical surface are focused on a point A on the central axis of the first lens and the second lens, the distance from the point A to the spherical surface is determined by the curvature radius of the spherical surface, and the point A is positioned on the beam splitting film of the beam splitting filter.
Further, the second lens is a self-focusing lens.
Furthermore, the first optical fiber head and the first lens, the beam splitting filter and the second lens, and the second lens and the second optical fiber head are connected by encapsulation.
Because the utility model discloses high performance optical coupler has adopted above-mentioned technical scheme, this optical coupler includes first optical fiber head promptly, first lens, first glass pipe, the second lens, the second glass pipe, the third glass pipe, beam splitting filter and second optical fiber head, be equipped with input optic fibre and reflection end optic fibre in the first optical fiber head, be equipped with transmission end optic fibre in the second optical fiber head, first lens nestification is in first glass manages, the second lens nestification is in the second glass manages, first glass manages and the second glass manages nestification in the third glass manages, first lens and the coaxial arrangement of second lens, beam splitting filter hugs closely the preceding terminal surface of locating the second lens, first optical fiber head aligns with first lens, the rear end face of second lens is located to the second optical fiber head. The optical coupler overcomes the defects of the traditional fused biconical taper optical coupler, has good flatness, is insensitive to temperature and polarization change, meets the typical indexes of a high-performance optical coupler, and is suitable for high-precision application occasions.
Drawings
The invention will be described in further detail with reference to the following drawings and embodiments:
FIG. 1 is a schematic diagram of a high performance optical coupler according to the present invention;
FIG. 2 is a schematic end view of a first fiber stub in the present high performance optical coupler;
FIG. 3 is a schematic end view of a second fiber stub in the present high performance optical coupler;
FIG. 4 is a schematic diagram of the optical path of the high performance optical coupler;
FIG. 5 is a schematic diagram of optical path misalignment in the high performance optical coupler;
FIG. 6 is a schematic diagram of polarization change of the high-performance optical coupler.
Detailed Description
Examples as shown in fig. 1, the high performance optical coupler of the present invention comprises a first fiber head 110, a first lens 120, a first glass tube 130, a second lens 140, a second glass tube 150, a third glass tube 160, a beam splitting filter 170, and a second fiber head 180, an input end optical fiber 111 and a reflecting end optical fiber 112 are arranged in the first optical fiber head 110, a transmission end optical fiber 181 is arranged in the second optical fiber head 180, the first lens 120 is nested in the first glass tube 130, the second lens 140 is nested in the second glass tube 150, the first glass tube 130 and the second glass tube 150 are nested in the third glass tube 160, the first lens 120 and the second lens 140 are coaxially arranged, the beam splitting filter 170 is closely attached to the front end surface of the second lens 140, the first fiber tip 110 is aligned with the first lens 120, and the second fiber tip 180 is disposed at the rear end face of the second lens 140.
Preferably, as shown in fig. 2, the end face of the first optical fiber head 110 is an inclined plane, the inclination angle of the inclined plane is 8 °, an inclined plane meridian is defined as a connecting line between an inclined plane high point and an inclined plane low point along the y direction, the input end optical fiber 111 and the reflection end optical fiber 112 are arranged along the meridian direction, the input end optical fiber 111 faces the inclined plane low point, and the rear end face of the first lens 120 is matched with the end face of the first optical fiber head 110.
Preferably, the inclination angle of the inclined plane of the first fiber head 110 and the inclination angle of the rear end face of the first lens 120 satisfy (n)f-1)α≈(nc-1) β, where α is the slope angle of the first fiber tip 110, β is the slope angle of the rear facet of the first lens 120, nfIs the refractive index of the core of the optical fiber, ncIs the first lens refractive index.
Preferably, as shown in fig. 3, the end surface of the second optical fiber head 180 is a slope, the slope angle is 8 °, a slope meridian is defined along the x direction, the transmission end optical fiber 181 is located at the center of the slope, and the slope meridian of the first optical fiber head 110 is orthogonal to the slope meridian of the second optical fiber head 180.
Preferably, an antireflection film is coated on an end surface of the beam splitting filter 170 adjacent to the first lens 120, a beam splitting film is coated on the other end surface, and a wedge angle is formed between the two coated end surfaces of the beam splitting filter 170, and the wedge angle is 0.7 °. The purpose of the wedge angle is to prevent "ghost images" of the reflected light, with the beam splitting film having a large transmission splitting ratio and a small reflection splitting ratio, such as 2% for 2/98 and 98% for transmission.
Preferably, the front end surface of the first lens 120 is a spherical surface, and the input light and the reflected light passing through the spherical surface are focused on a point a on the central axis of the first lens 120 and the second lens 140, the distance from the point a to the spherical surface is determined by the radius of curvature of the spherical surface, and the point a is located on the beam splitting film of the beam splitting filter 170.
Preferably, the second lens 140 is a self-focusing lens.
Preferably, the first optical fiber head 110 and the first lens 120, the beam splitting filter 170 and the second lens 140, and the second lens 140 and the second optical fiber head 180 are connected by using an encapsulation 190. The fixing mode has the advantages that lateral displacement is not easy to generate between the optical fiber head and the lens due to temperature change, so that loss is not easy to change along with the temperature change, and the light splitting ratio is not sensitive to the temperature change. By this arrangement, the TDL of the present optical coupler can meet the <0.05dB requirement.
As shown in fig. 4, the dashed line is the central axis of the first lens 120 and the second lens 140, when the first fiber head 110 is aligned with the first lens 120, the fiber head is off-axis with respect to the first lens by about 10 μm, and the input end fiber 111 and the reflective end fiber 112 are located on the back focal plane of the first lens. The bevel angle α of the first fiber head 110 and the rear end face angle β of the first lens 120 satisfy a certain approximate relationship. Assuming that the bevel angle α of the first fiber head 110 is 8 °, the back facet angle β of the first lens 120 is about 5 °. This allows both the input ray 121 and the reflected ray 122 in the first lens 120 to travel horizontally in the z-direction and to be symmetric about the central axis. The front face 123 of the first lens 120 is spherical and converges light such that the input light 121 and the reflected light 122 are focused at a point a on the central axis. The distance from point a to the front face 123 of the first lens 120 is determined by the radius of spherical curvature, which is about 2mm assuming a radius of spherical curvature of 1.4.
The beam splitting filter 170 is disposed on the front end face 142 of the second lens 140, the end face 172 of the beam splitting filter is coated with a beam splitting film and faces and adheres to the front end face 142 of the second lens, and the end face 171 is coated with an antireflection film and faces the first lens 120. The front and rear positions of the beam splitting filter 170 are adjusted so that the point a is located right on the beam splitting film of the end surface 172, and the input light 121 is split by the beam splitting film into the reflected light 122 and the transmitted light 141.
The flatness index of the optical coupler is related to the oscillation amplitude and the oscillation period of the optical spectrum, and the two indexes depend on the interference effect between two parallel end surfaces on an optical path, particularly the reflectivity and the distance.
A wedge angle, such as 0.7 °, is provided between the end surface 171 and the end surface 172 of the beam splitting filter 170 to avoid interference effects between the two end surfaces. The front end surface 123 of the first lens 120 is a spherical surface, and interference does not occur between the spherical surface 123 and the end surface 171. The end surface 172 coated with the beam splitting film is tightly attached to the front end surface 142 of the second lens 140, and although the two end surfaces are parallel, because the distance between the two end surfaces is micrometer, the spectral oscillation period is also micrometer, and the oscillation period is far larger than the working wavelength range (1260-1620 nm) of the optical coupler. The interference effect between the end face 172 and the end face 142 does not degrade the flatness index of the optical coupler. With this arrangement, the Ripple of the optocoupler can satisfy <0.05 dB.
The second lens 140 is a self-focusing lens, and the lens length is set to 0.248P. The transmitted ray 141 starts at the central axis of the lens and follows 1/4 sine waves in the lens. That is, the transmitted rays emerge horizontally in the z-direction, with the rays being about 50 μm off-axis. The second fiber tip 180 is aligned with the transmitted light ray 141 and the fiber 181 is positioned at the back focal plane of the second lens 140, again about 50 μm off-axis.
If point a is not located on the beam splitting film of end face 172, as shown in fig. 5, the origin of transmitted light ray 141 in second lens 140 is no longer on the central axis, which can create a "misalignment" effect. The transmission light path is complicated by slight misalignment effects. For example, the end surface 172 is located between the spherical surface of the first lens 120 and the point a, and the incident point of the input light ray 121 on the end surface 172 is lower than the central axis, so that the transmitted light ray 141 exits from the second lens 140 at an elevation angle. The second fiber tip 180 must also be rotated through a corresponding angle when aligned with the transmitted light 141. In other words, the change in the position of the origin of the transmitted light 141 is compensated by the angle of the second fiber head 180.
As shown in FIG. 6, the first lens 120 back end surface meridian and the first fiber tip 110 slope meridian are both in the yz plane, while the second lens 140 back end surface meridian and the second fiber tip 180 slope meridian are parallel, the latter two meridians being orthogonal to the former two meridians. Input end fiber 111 and reflective end fiber 112 are aligned in the yz plane. This arrangement is advantageous in that the PDL of the optical coupler can be minimized, as described in detail below:
the polarization state in the yz plane is defined as p-polarization and the polarization state in the xy plane is defined as s-polarization. When the input light 121 sequentially passes through the inclined plane of the first fiber head 110, the rear end face and the front end face of the first lens 120, and the end face 171 of the beam splitting filter 170, p-polarization is enhanced. The input light 121 is reflected by the beam splitting filter 170 to become the reflected light 122, and s-polarized and enhanced at the end surface 172. The reflected light 122 sequentially passes through the end surface 171 of the beam splitting filter 170, the front end surface and the rear end surface of the first lens 120, and the inclined surface of the first fiber head 110, and is p-polarized and enhanced. The p-emphasis and s-emphasis in the reflected light path partially cancel. Similarly, input light ray 121 becomes transmitted light ray 141 after passing through beam splitting filter 170, with p-polarization enhancement at end face 172. The transmitted light 141 is p-polarized and s-polarized when passing through the front end face 142 of the second lens 140 and the back end face of the second fiber head 180. The p-emphasis and s-emphasis in the transmitted light path partially cancel.
In addition, the beam splitting film of the beam splitting filter 170 has a large transmission splitting ratio and a small reflection splitting ratio. The advantage of this arrangement is that the number of coating layers is reduced, the less the number of coating layers, the less the polarization dependence.
With the above arrangement, the PDL value of the present optical coupler can satisfy <0.01 dB.
The coordinate systems mentioned above are identified by the drawing.
The optical coupler completely meets typical indexes of high-precision application occasions, has good flatness, is insensitive to temperature and polarization change, and improves the application performance of the optical coupler.
Claims (8)
1. A high performance optical coupler, characterized by: this optical coupler includes first optical fiber head, first lens, first glass pipe, second lens, second glass pipe, third glass pipe, beam splitting filter and second optical fiber head, be equipped with input optic fibre and reflection end optic fibre in the first optical fiber head, be equipped with transmission end optic fibre in the second optical fiber head, first lens nest in the first glass manages, second lens nest in the second glass manages, first glass pipe and second glass pipe nest in the third glass manages, first lens and the coaxial arrangement of second lens, beam splitting filter hugs closely and locates the preceding terminal surface of second lens, first optical fiber head with first lens are aimed at, second optical fiber head locates the rear end face of second lens.
2. The high performance optical coupler of claim 1, wherein: the end face of the first optical fiber head is an inclined plane, the inclination angle of the inclined plane is 8 degrees, an inclined plane meridian is defined as a connecting line between an inclined plane high point and an inclined plane low point along the y direction, the input end optical fiber and the reflection end optical fiber are arranged along the meridian direction, the input end optical fiber faces the inclined plane low point, and the rear end face of the first lens is matched with the end face of the first optical fiber head.
3. The high performance optical coupler of claim 2, wherein: the inclined plane inclination angle of the first optical fiber head and the inclination angle of the rear end face of the first lens meet (n)f-1)α≈(nc-1) β, where α is the slope angle of the first fiber tip, β is the slope angle of the rear facet of the first lens, nfIs the refractive index of the core of the optical fiber, ncIs the first lens refractive index.
4. The high performance optical coupler of claim 2, wherein: the end face of the second optical fiber head is an inclined plane, the inclination angle of the inclined plane is 8 degrees, the inclined plane meridian is defined along the x direction, the optical fiber at the transmission end is positioned in the center of the inclined plane, and the inclined plane meridian of the first optical fiber head is orthogonal to the inclined plane meridian of the second optical fiber head.
5. The high performance optical coupler of claim 1, wherein: the end face of the beam splitting filter adjacent to the first lens is plated with an antireflection film, the other end face of the beam splitting filter is plated with a beam splitting film, a wedge angle is arranged between the two film-plated end faces of the beam splitting filter, and the wedge angle is 0.7 degrees.
6. The high performance optical coupler of claim 5, wherein: the front end face of the first lens is a spherical surface, input light rays and reflected light rays passing through the spherical surface are focused on a point A on a central axis of the first lens and the second lens, the distance between the point A and the spherical surface is determined by the curvature radius of the spherical surface, and the point A is positioned on a beam splitting film of the beam splitting filter.
7. The high performance optical coupler of claim 1, wherein: the second lens is a self-focusing lens.
8. The high performance optical coupler of claim 1, wherein: the first optical fiber head and the first lens, the beam splitting filter and the second lens, and the second lens and the second optical fiber head are connected by encapsulation.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202021628795.8U CN213210538U (en) | 2020-08-07 | 2020-08-07 | High performance optical coupler |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202021628795.8U CN213210538U (en) | 2020-08-07 | 2020-08-07 | High performance optical coupler |
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| CN213210538U true CN213210538U (en) | 2021-05-14 |
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| CN202021628795.8U Active CN213210538U (en) | 2020-08-07 | 2020-08-07 | High performance optical coupler |
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