KR101227182B1 - Optical module using lenz having coated concave plane - Google Patents

Abstract

PURPOSE: An optical module using lens which has coated concave plane is provided to reduce the cost and simplify the structure without using GRIN lens as well as filter and degradation of the property. CONSTITUTION: An optical module using lens which has coated concave plane uses a lens(1) coated with a filter layer on the concave plane(2). A lens such as a Meniscus lens comprises a concave plane on one side and a convex plane(3) on the opposite side. A concave plane of the lens which forms a sphere or an ellipse deposits a thin film of WDM or TAP filter on the surface and a convex plane which is coated with AR(Anti-Reflection) coating forming in an aspheric shape.

Description

OPTICAL MODULE USING LENZ HAVING COATED CONCAVE PLANE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical module using a lens having a coated concave surface, and more particularly, a thin film having a WDM or TAP function is coated on a lens surface having a concave surface, and a predetermined amount of light input from an input terminal is applied to the lens surface. A wavelength or a predetermined amount of light is reflected, and the remaining light transmitted through the concave surface is transmitted through the convex surface in the form of parallel light or focused light, thereby simplifying the structure without using the GRIN lens and filter and inexpensive without deterioration of characteristics. The present invention relates to an optical module using a lens having a coated concave surface that can achieve anger.

The competitiveness of the nation in the information society of the 21st century is only possible when the optical communication infrastructure is expanded and the public can easily access and utilize it. To date, advances in optical communications technology have changed to accommodate a wide range of communications network scalability and the ability to reserve services for responding to changing demands. To meet this trend, optical communications systems are expected to achieve higher speed, wavelength division multiplex (WDM), and integration. And technology development in various fields is required.

Therefore, the technology for the optical communication device that can satisfy the high capacity and ultra high speed of the transmission signal is rapidly developing. Especially, the optical communication device for controlling the optical path is WDM coupler, hybrid isolator. It is in demand as a key technology used in Nap Photodiode (TAP PD).

The WDM coupler technology, which combines multiple wavelengths and transmits them to one optical fiber, is a core technology for adding and dropping wavelengths. FIG. 1 illustrates the structure of a conventional WDM coupler. Referring to FIG. 1, a typical WDM coupler receives wavelengths of l ₁ , l ₂ , --- l _k , and --- l _n from the input terminal 21, and the input optical signal is converted into parallel light so that the WDM filter 27 In this case, the l _k wavelength is transmitted, and the remaining l ₁ , l ₂ , --- l _n wavelengths are reflected, and the reflected light is passed through the GRIN lens (26, Graded Index lens) on the input terminal 21 side. The l _k light that is focused by the optical fiber and the remaining transmitted light is finally focused through the GRIN lens 28 on the output end 30 to the optical fiber of the output end 30. Conventionally, in order to focus on three optical fibers simultaneously at most of the input end 21, the reflecting end 22, and the output end 30, in particular, in order to optically couple the input end 21 and the reflecting end 22, the input end 21 is inevitably required. The method of adjusting the angle of the WDM filter 27 under parallel light through the side GRIN lens 26 was used. In this structure, two expensive GRIN lenses 26 and 28 are used, and a high precision glass tube 24 is used to align the glass capillary 23 and the GRIN lens 26. It is used and has a structure surrounded by a metal tube 25 on the outside thereof. On the output end 30 side, the GRIN lens is aligned by the glass tube 29.

As described above, the WDM coupler using the GRIN lens has a structure that enables a small coupling loss and a high stability in productivity. However, a high precision component such as a GRIN lens is used, and each process uses an alignment process and an epoxy ( epoxy) Because of the bonding process, the manufacturing process of the device is difficult and low cost is difficult.

The present invention was conceived by recognizing the above point, the object of the present invention is to coat a thin film having a WDM or TAP function on the lens surface having a concave surface, the predetermined wavelength or a predetermined amount of light input from the input end to the lens surface Light is reflected, and the remaining light transmitted through the concave surface is transmitted through the convex surface in the form of parallel light or focused light, simplifying the structure without using the GRIN lens and filter and lowering the price without deterioration of characteristics. It is to provide an optical module using a lens having a coated concave surface.

In order to achieve the above object, an optical module using a lens having a coated concave surface according to the present invention is provided in the optical module using a lens having a coated concave surface in which a coated concave lens is embedded. The optical signal reflected from the concave lens surface coated with the WDM or TAP function is focused on the optical fiber which is the output part, and the transmitted optical signal is converted into parallel light or condensed light on the convex lens surface and the optical fiber which is the output part It is characterized by being focused on.

In addition, the optical module using a lens having a coated concave surface according to the present invention, by using a three-core capillary tube to adjust the angle of the input fiber (input fiber) and the output fiber (out fiber) to maximize the optical coupling efficiency It is characterized by.

In addition, the optical module using a lens having a coated concave surface according to the invention, it characterized in that to fix the dual core fiber and single core fiber with the coated lens using the align and laser welding equipment.

In addition, the optical module using a lens having a coated concave surface according to the present invention, the WDM filter that reflects at least one or more of l1, l2, ... lk, ... ln as the input optical signal, the rest of the WDM filter It is used to construct a WDM coupler using a coated lens.

In addition, an optical module using a lens having a coated concave surface according to the present invention is characterized in that it is used to configure a WDM hybrid isolator by mounting an optical isolator between the lens and the SCF.

In addition, the optical module using a lens having a coated concave surface according to the present invention, TAP PD using a lens coated with a TAP filter that transmits any light of only 1 ~ 99% to the input optical signal and reflects the rest. It is characterized by being used to construct.

The optical module using a lens having a concave surface coated according to the present invention by the above configuration is coated with a thin film having a WDM or TAP function on the lens surface having a concave surface, the predetermined amount of light input from the input end to the lens surface A wavelength or a predetermined amount of light is reflected, and the remaining light transmitted through the concave surface is transmitted through the convex surface in the form of parallel light or focused light, thereby simplifying the structure without using the GRIN lens and filter and inexpensive without deterioration of characteristics. Has the advantage of being angry.

In particular, the optical module using a lens having a coated concave surface according to the present invention has a simpler structure than the optical element of the structure using the conventional GRIN lens and WDM filter and not only simplify the manufacturing process but also maximize the optical coupling efficiency, optical Minimize losses, reduce component count, maintain optical device characteristics, and reduce manufacturing costs.

In addition, the optical module using a lens having a coated concave surface according to the present invention by replacing the conventional epoxy process used in the optical device of the structure using the conventional GRIN lens and WDM filter by laser welding (laser welding) It has the advantage of ensuring reliability.

1 is a cross-sectional view illustrating a structure of a dual fiber collimator using a conventional GRIN lens and a WDM filter and a WDM coupler using the same
2 is a conceptual diagram showing an optical system structure of an optical module using a lens having a coated concave surface according to an embodiment of the present invention
3A is a conceptual diagram illustrating an optical system structure of a focusing beam of an optical module using a lens having a coated concave surface according to an embodiment of the present invention;
3B is a conceptual diagram illustrating an optical system structure of a collimating beam of an optical module using a lens having a coated concave surface according to another embodiment of the present invention.
4 is a conceptual diagram illustrating a structure of a dual core fiber in which an optical fiber of an optical fiber is inclined relative to an optical fiber of an input optical fiber in an optical module using a lens having a coated concave surface according to another embodiment of the present invention;
5 is a structural diagram showing an example of (a) WDM coupler, (b) hybrid isolator and (c) TAP PD using an optical module using a lens having a coated concave surface according to an embodiment of the present invention

In the optical module using a lens having a coated concave surface according to the present invention, after the filter layer is coated on the concave surface, the light emitted from the input terminal is separated or reduced, and then the reflected light is focused onto the reflecting stage. The transmitted light is an optical component that focuses to an output terminal, and is used for fabricating optical devices such as a WDM coupler, a hybrid isolator, and a TAP PD.

Hereinafter, with reference to the embodiment shown in the drawings will be described in more detail an optical module using a lens having a coated concave surface according to the present invention.

2 is a conceptual diagram illustrating an optical system structure of an optical module using a lens having a coated concave surface according to an embodiment of the present invention, Figure 3a is a lens having a coated concave surface according to an embodiment of the present invention 3 is a conceptual diagram illustrating an optical system structure of a focusing beam of an optical module, and FIG. 3B is a conceptual diagram illustrating an optical system structure of a collimating beam of an optical module using a lens having a coated concave surface according to another embodiment of the present invention. 4 is a conceptual diagram illustrating a structure of a dual core fiber in which the reflection optical fiber is inclined relative to the input optical fiber in an optical module using a lens having a coated concave surface according to another embodiment of the present invention, and FIG. A structural diagram illustrating an example of (a) WDM coupler, (b) hybrid isolator, and (c) TAP PD using an optical module using a lens having a coated concave surface according to an embodiment of the present invention.

2, the optical module using a lens having a coated concave surface according to an embodiment of the present invention is characterized by using a lens 1 coated with a filter layer on the concave surface (2, concave plane). The lens 1 is a concave and convex surface 3 on the opposite side as a concave plane 2 on one side as a meniscus lens. The concave surface 2 of the lens 1 has a spherical or ellipse shape, and a WDM or TAP filter is deposited on the surface thereof, and the convex surface 3 has an AR coating in an aspheric shape. (Anti-reflection coating) is preferable.

In the case of an ellipse in which the concave surface 2 of the lens 1 has a long axis a and a short axis b, the light incident at the focus F (c, 0) is reflected at the concave surface 2 to focus F (-c, 0). The shape of the concave surface 2 and the arrangement of the incidence end 7 and the reflection end 8 are designed to focus on. 2 illustrates an embodiment in which the convex surface 3 of the lens 1 is designed to focus light at the output end 6 by collecting light that exceeds the concave surface 2. If the distance between the focal point F (c, 0) and F (-c, 0) of the concave surface 2, that is, the distance between the input terminal 7 and the reflecting terminal 8 is very small compared to the distance of the long axis a, the ellipse is spherical. Even the design of the sphere does not affect the coupling efficiency.

The light incident through the input terminal 7 is focused on the reflection stage 8 by reflecting a specific light or a part of the specific light according to a thin film filter coated on the concave surface 2 of the lens 1. The light transmitted through the coated thin film filter is focused through an aspherical lens formed on the convex surface 3 of the lens 1 and input to the optical fiber of the output terminal 6. The convex surface 3 of the lens 1 is preferably AR coated to minimize reflection loss.

2 and 3A, the centerline 4 of the light incident on the concave surface 2 has an angle of θ ₀ with respect to the vertical line and the centerline 5 of the light reflected by the filter of the concave surface 2 is The concave surface 2 has a spherical or elliptical structure with two foci, such that the angle formed with respect to the vertical line is equal to the angle of light incident at θ ₀ . The end of the optical fiber has a structure inclined at an inclination angle (θ ₃ ) of 6 degrees to 8 degrees in order to satisfy a return loss of 60 dB or more, and due to the inclination angle (θ ₃ ), The output light has a specific angle that satisfies Equation 1 according to the refractive index of the optical fiber. By using this property, when the angle of the optical fiber of the input terminal 7 is inclined to θ ₁ , the light output from the optical fiber of the input terminal 7 has a radiation angle satisfying θ ₄ .

[Equation 1]

n _o * sinθ ₀ = n ₁ * sinθ ₁

However, n _o , n ₁ : refractive index of air and optical fiber material, θ _0, θ ₁ : incidence angle of air and optical fiber

On the other hand, the light reflected from the filter-coated concave surface 2 is incident to the reflecting end 8 at an angle of θ ₀ , where the optical fiber of the reflecting end 8 is θ ₂ to maximize the optical coupling efficiency. Tilt by, which satisfies the following equation (2).

&Quot; (2) "

θ ₂ = θ ₁ + 2θ ₀

Meanwhile, FIG. 3A is a conceptual diagram illustrating an optical system structure of a focusing beam of an optical module using a lens having a coated concave surface according to an embodiment of the present invention, and the optical system illustrated in FIG. 3A is a concave surface coated with a filter ( 2) the lens 1, the dual core fiber (DCF) and the single core fiber (SCF) are composed of an optical system of focusing beam. The distance between the lens 1 and the DCF is L ₁ , the distance between the lens 1 and the SCF is L ₂ , and a single mode fiber having a radiation angle θ ₄ is used to form the input terminal 7 and the output terminal 6. The structure is output from the incident port at an angle of q0 with respect to the center line, and is reflected and input into the reflective port. Light passing through the lens is incident on the output port.

In FIG. 3B, the convex plane 3 has the same structure as that of FIG. 2 and is designed to form parallel light, thereby making the light output to the output port into parallel light. Such an optical structure may be used for an optical module requiring parallel light, such as an optical switch and an optical attenuator.

4 shows the structure of the output port having a constant angle with respect to the incident port in order to increase the optical coupling efficiency. A general dual core fiber has two optical fibers in parallel to the two-hole glass capillary, but to tilt the optical fiber at the reflection port, three-hole glass capillary (9) can be used to input the optical fiber. The optical fiber 7 of the port is fixed, and the optical fiber 8 of the reflective port is fixed using epoxy to form an angle of 2θ ₂ . At this time, the tilt angle of the reflecting port is determined according to the length L of the 3-hole glass capillary and the length of the inner rectangle. The cross section 10 of the incidence port and the reflecting port is flat angle polished at an angle of θ ₃ and is AR coated to maximize the return loss and minimize the insertion loss. Light incident at an angle of θ ₀ with respect to the center line of the optical fiber 7 of the input port is reflected by the coating of the concave plane 2 to be equal to the center line of the optical fiber 8 of the reflective port. Since the light is incident at an angle of _0, the light coupling efficiency can be maximized.

5A is a structural diagram of a WDM-coupler using a lens structure coated with a WDM filter using the present invention. The wavelength of l1, l2 --- lk, --- ln enters into the input optical port 8, and the input optical signal is transmitted through the lk wavelength in the WDM filter 2 and the remaining l1, l2, --- ln wavelengths The reflected and reflected light is focused on the optical fiber of the reflective port 7 and the remaining transmitted lk light is focused on the output port 16 to the output port. The WDM filter 2 was deposited on the concave plane of the lens 1 using an e-beam evaporator, and the AR coating was deposited on the convex plane 3 on the opposite side. The WDM filter coated lens (1) is welded to the stainless steel 304 barrel (14) so that it is 3-point symmetrical with a laser welder, and the dual core fiber (11) with an input port and a reflection port has an angle of θ _0. Bond with epoxy using a glass capillary holder (12) made to achieve In addition, the SCF holder 17 is manufactured such that the single core fiber 16 of the reflective port has an angle of θ ₀ like the DCF 11. The dual core fiber 11 fabricated as described above uses a laser welding machine to input light of l1 to the input port 8 with the optical power of Po while the light output value of Pr output to the reflection port 7 is maximized. An optical alignment is made to weld the spacer 13 portion, the DCF barrel 12 and the lens barrel 14 at this point. Then, the SCF 16 of the output port is similarly inputted with lk light into the input port 8 with Po optical power, and the laser beam is fixed by aligning the light output value of Pt outputted to the output port 16 to the maximum. do. The optical alignment performs x, y, z axis movement and z axis rotation with respect to lenses coated with DCF and SCF, respectively. In the case of the conventional WDM coupler using the GRIN lens, in order to perform optical coupling between the input port and the reflective port, the WDM filter is fixed to the GRIN lens after optical alignment by adjusting the angle of the WDM filter. Epoxy is easily deformed at high temperature and high humidity, which makes it difficult to maintain long-term reliability. In addition, the WDL (wavelength dependant loss), which is an important characteristic of the WDM coupler, is caused by the angle of incident beam of the WDM filter of the incident light, and the filter coated on the concave plane of the present invention essentially has zero AOI. WDL can be solved. As in the present invention, the WDM filter is directly deposited on the lens, and instead of using epoxy in a fixed manner, laser welding is used to simplify the process and improve long-term reliability of satisfying the high temperature and high humidity characteristics of the device. It can satisfy the characteristics of wavelength dependant loss.

FIG. 5B is a structural diagram showing the function of the hybrid in-line isolator by inserting the optical isolator 18 between the lens 2 and the output end 16 while having the structure of FIG. By placing the optical isolator, the lk optical signal output through the WDM filter-coated lens is incident to the output port and conversely, the optical signal reflected from the output port cannot return to the input port 11.

FIG. 5C shows a concave plane of a lens with a TAP filter 2 having a function of transmitting only a predetermined amount of light and reflecting the remaining light instead of the WDM coating of FIG. 5A. ) And a TAP PD for power monitoring using a mini photo diode (20) instead of an optical fiber at the output port is shown. Welding of the dual core fiber and the lens was performed in the same manner as in FIG. 5 (a). Since the coupling efficiency of the monitoring photodiode is about 80 micron in the active area of the light receiving device, the structure between the photodiode and the lens barrel instead of the optical alignment is provided. It was produced in a manner that combines using.

As mentioned above, WDM or TAP filter is coated on the concave plane without using the existing GRIN lens and filter, and it uses the lens that creates the focused light on the convex plane. By using dual core fiber with reflective port inclined at an angle, WDM coupler, Hybrid isolator, and TAP PD can be manufactured.

The WDM coupler illustrated in FIG. 5A is specifically manufactured as follows. The lens L1 was 5 mm, the lens inner diameter was 1.8 mm, the outer diameter was 2.8 mm, the height was 1.6 mm, and the L2 was 6 mm. The concave plane is coated with a WDM filter that transmits the 1550 nm band and reflects the 1310 nm wavelength band, and an AR coating of the 1550 nm wavelength band is applied to the convex plane. The dual core fiber capillary uses a glass tube with an outer diameter of 1.8mm, a length of 5mm, and a capillary size of 0.378 x 0.127mm, the pitch P between the two optical fibers is 0.125mm, and the reflective port optical fiber is inclined 0.43 degrees compared to the incident port optical fiber. The optical fibers of the and reflective ports were polished at an inclined angle of 8 degrees (θ ₃ ), and the end face 10 was AR coated in the band 1310 ~ 1550nm. The barrel of the dual core fiber was made so that the dual core fiber was inclined at 2.94 degrees (θ ₁ ) so that light was incident and emitted at an angle of 0.71 degrees (θ ₀ ) to the concave plane of the lens. Corning's SMF-28 fiber has an emission angle (θ ₄ ) of 5.4 degrees and an effective beam diameter of 1.4mm. The outer diameter of the fabricated WDM coupler is 3.8mm and the total length is 28mm. Similarly, single core fiber was AR coated at 1.8mm in diameter, 5mm in length and 8 degree after polishing, and its slope was 2.94 degree.

The assembly sequence is 3 point welding of WDM filter coated lens to the lens barrel with laser welder. After aligning the dual core fiber to the coated lens to maximize the amount of light output to the reflective port, -point welded. At this time, post welding shift showed a similar tendency to welding LD and optical fiber.

The insertion loss of 0.5dB was generated at the reflection port when 1310nm light was inputted 0dBm at the input port and the maximum optical coupling efficiency was arranged. Insertion of 1550nm light into the input port at 0dB resulted in an insertion loss of 0.4dB at the output port. The return loss is more than 60dB, and WDM-coupler can be manufactured which shows similar characteristics compared with the case of using GRIN lens.

Hybrid isolator shown in Figure 5 (b) is specifically produced as follows. The lens and lens barrel, dual core fiber, and single core fiber of the same standard as in FIG. 5 (a) were used. In the case of only lens coating, a 1550 nm wavelength band was transmitted and a 1490 nm wavelength band was coated with a reflective filter. A single stage isolator was used. The combination of the isolator and the lens barrel was 3-point welded using a laser welder and obtained the same characteristics as the device using the GRIN lens.

The TAP PD shown in FIG. 5C is specifically manufactured as follows. A lens, a lens barrel, and a dual core fiber of the same standard as in FIG. 5 (a) were used, and a filter coated lens was used that transmits less than 2% of the wavelength at 1550 nm and reflects the rest. The photodiode of the receiver uses a mini PIN PD with a flat window cap with a diameter of 1.9mm. Instead of aligning the single core fiber during assembly, the photodiode was monitored after aligning to the point where the responsivity is maximized while monitoring the responsitivity of the PD. The insertion loss of the reflection port is 0.5dB and the responsitivity is 0.95, which is similar to the conventional TAP PD. While the outer diameter of the existing mini TAP PD is only 3.2mm and the length is less than 20mm, it is necessary to miniaturize the outer diameter of the device according to the present invention to 3.8mm and 26mm in the future.

5 (a) to (c) above, it was confirmed that the optical module using the lens having the coated concave surface according to the present invention can obtain the same characteristics as the device using the conventional GRIN lens. By lowering the cost and simplifying the manufacturing process, low cost is achieved, and laser welding is performed without using epoxy, and the long term reliability such as high temperature and high humidity environment is excellent.

As described above, a WDM coupler, a hybrid isolator, and a TAP PD may be manufactured using an optical module using a lens having a concave surface coated with a WDM filter or a TAP filter according to the present invention without using a conventional GRIN lens. Compared with the conventional optical modules, they can be manufactured at low cost without any degradation of characteristics such as insertion loss and return loss. Table 1, Table 2, Table 3 compares the performance of the optical module using the lens with the coated concave surface according to the present invention by the raw material, manufacturing process and performance of the device using the conventional GRIN lens. Table 1 summarizes the raw materials used, Table 2 summarizes the manufacturing process, and Table 3 compares the performance.

Existing WDM coupler Invention of WDM coupler Remarks dual core fiber dual core fiber (2 ^nd fiber tilt) demerit single core fiber single core fiber same GRIN lens 2ea meniscus lens 1ea merit glass capillary 2ea none merit metal housing metal housing same WDM filter WDM filter coating on lens demerit

Existing WDM coupler Invention of WDM coupler Remarks Fixing of DCF to GRIN lens Fixing of DCF to coated lens same Fixing of WDM filter to GRIN lens none merit Fixing of SCF to DCF Fixing of SCF to DCF same

Existing WDM coupler Invention of WDM coupler Remarks Insertion loss <0.4 dB same Return loss > 60dB same PDL, WDL <0.2 dB same dimension Dia. <4.0mm, length <30mm merit

The optical module using the lens having the coated concave surface described above and shown in the drawings is only one embodiment for carrying out the present invention, and should not be construed as limiting the technical idea of the present invention. The scope of protection of the present invention is defined only by the matters set forth in the claims below, and the embodiments which have been improved and changed without departing from the gist of the present invention will be apparent to those skilled in the art. It will be said to belong to the protection scope of the present invention.

1 lens (coated meniscus lens)
2 concave plane
3 convex plane
4 incident light
5 reflected light
6 output
7 entrance
8 reflection stage
9 glass core capillary
10 polished plane
11 dual core fiber (DCF)
12 DCF housing
13 DCF ring
14 lens housing
15 SCF ring
16 single core fiber (SCF)
17 SCF housing
18 optical isolator
19 photodiode
21 input
22 reflection
23 glass core capillary
24 glass tube
25 metal tube
26 GRIN Lens
27 WDM Filter
28 GRIN Lens
29 glass tube
30 single core fiber (SCF) output

Claims (6)

In an optical module using a lens having a coated concave surface with a coated concave lens,
The concave surface of the concave lens is coated with a WDM filter or a TAP filter which transmits only a certain amount of light with respect to light of a specific wavelength and reflects the remaining light.
The optical signal reflected from the concave surface among the optical signals incident on the optical fiber as the input unit is focused on the optical fiber as the output unit, and the optical signal passing through the concave surface is converted into parallel light or condensed light at the convex surface and converged to the optical fiber as the output unit. Optical module using a lens having a coated concave surface, characterized in that. The method of claim 1,
The angles of the input fiber and the output fiber are θ ₁ and θ ₂ , respectively, and are reflected light emitted from the input fiber and reflected from the concave surface to the output fiber. When the reflection angle of is θ ₀ ,
Using a 3-core capillary tube to adjust the angle of the input fiber and the output fiber to satisfy the relationship of θ ₂ = θ ₁ + 2θ ₀ to maximize the optical coupling efficiency Optical module using a lens having a. The method according to claim 1 or 2,
An optical module using a lens having a coated concave surface, wherein the dual core fiber and the single core fiber are fixed to the coated lens by using an alignment and laser welding device. The method according to claim 1 or 2,
Characterized in that it is used to construct a WDM coupler using a lens coated with a WDM filter that reflects at least one or more of l1, l2, .... lk, .... ln as an input optical signal and transmits the rest. Optical module using a lens having a coated concave surface. The method according to claim 1 or 2,
An optical module using a lens having a coated concave surface, which is used to construct a WDM hybrid isolator by mounting an optical isolator between the lens and the SCF. The method according to claim 1 or 2,
Optical module using a lens having a coated concave surface, which is used to construct a TAP PD using a TAP filter coated lens that transmits any light of 1 to 99% and reflects the rest of the input optical signal. .

Images