JP6878055B2 - Optical circuit and optical module - Google Patents

Description

The present disclosure relates to optical circuits and optical modules.

An optical circuit (PLC (Planar Lightwave Circuit)) has been proposed (see, for example, Patent Document 1). The optical circuit of Patent Document 1 adjusts the angle of the waveguide section so that the light is not captured in the waveguide section and further, the light is prevented from being recombined from one branch section to the other branch section. Set.

Light incident on optical circuits such as PLC (Planar Lightwave Circuit) and SiP (System in a Package) is reflected at the ends of wavelength plates, waveguide edges, lenses, PDs (Photodiodes), LDs (Laser Diodes), etc. , Radiates and scatters and propagates as leaked light in the cladding and substrate. These leaked lights propagate in all directions in the optical circuit, enter the optical component connected to the optical circuit, and deteriorate the characteristics of the optical component. Taking an optical communication module using an optical circuit as an example, the leaked light scattered by the optical circuit goes toward the monitor PD from all directions, causing deterioration of the light receiving sensitivity of the monitor PD.

Japanese Unexamined Patent Publication No. 2014-211553

An object of the present disclosure is to reduce leakage light in an optical circuit and prevent deterioration of characteristics of optical components.

Since the end face in the entrance / exit direction of the optical circuit is a surface that is optically coupled to the external circuit, end face treatment is performed, but the end face treatment is particularly performed on the surface that has no entrance / exit end of the waveguide and no optical coupling with the outside. It wasn't done. Therefore, in the present disclosure, the end face having no optical coupling with the outside is obliquely processed to guide the scattered leaked light to the outside of the optical circuit.

Specifically, the optical circuit of the present disclosure is
A waveguide whose core is covered with a clad,
Leaked light leaked from the core to the clad by inclining at least a part of the end face where the waveguide end is not arranged among the end faces arranged substantially perpendicular to the surface on which the waveguide is arranged. With a reflector that reflects the light toward the outside of the optical circuit,
To be equipped.

The inclination of the reflecting portion may be applied to the entire end face of the end face where the waveguide end is not arranged.

The angle formed by the inclined end surface of the reflecting portion and the surface parallel to the surface on which the waveguide is arranged may be approximately 45 °.

A non-reflective portion which is arranged on the optical path of the leaked light emitted from the optical circuit in the outer peripheral surface of the optical circuit and absorbs the leaked light emitted from the optical circuit may be further provided.

The optical module of the present disclosure is arranged on an optical path of the optical circuit of the present disclosure, a housing covering the optical circuit, and light leaked from the optical circuit in the inner wall surface of the housing, and the light is described. It includes a non-reflective part that absorbs the leaked light emitted from the circuit.

The above disclosures can be combined as much as possible.

According to the present disclosure, it is possible to reduce the leaked light in the optical circuit and prevent the deterioration of the characteristics of the optical component.

This is an example of an optical module according to this embodiment. This is an example of the reflecting unit in the present embodiment. This is another example of the installation of the non-reflective portion in the present embodiment.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The present disclosure is not limited to the embodiments shown below. Examples of these implementations are merely examples, and the present disclosure can be implemented in various modifications and improvements based on the knowledge of those skilled in the art. In addition, the components having the same reference numerals in the present specification and the drawings shall indicate the same components.

FIG. 1 shows an example of an optical module according to this embodiment. In the optical module according to the present embodiment, the optical circuit 2 according to the present embodiment is arranged in the housing 9. In the present embodiment, as an example of the optical module, a case where the optical module is a receiving module that receives a phase-modulated optical signal will be described.

The optical module according to this embodiment includes an optical circuit 2, a monitor PD 5, a light receiving element 6, a bias differential detector 7, a signal processing unit 8, and a housing 9. The optical circuit 2, the monitor PD5, the light receiving element 6, the bias differential detector 7, and the signal processing unit 8 are covered with a housing 9.

The optical signal transmitted by the optical fiber 11 is incident on the optical circuit 2. The optical circuit 2 includes a waveguide whose core is covered with a cladding (not shown), and uses the waveguide to guide an optical signal from the optical fiber 11 to the monitor PD 5 and the light receiving element 6. The monitor PD5 receives the monitor light incident from the optical fiber 11 and observes the intensity of the optical signal. The light receiving element 6 receives an optical signal illuminated from the optical fiber 11 and converts it into an electric signal. The bias differential detector 7 detects the difference between the electric signals converted by the light receiving element 6. The signal processing unit 8 demodulates the optical signal using the output signal from the bias differential detector 7.

A first end face 21, a second end face 22, a third end face 23, and a fourth end face 24 are arranged on an outer peripheral surface substantially perpendicular to the surface on which the waveguide of the optical circuit 2 is formed. A waveguide end for input / output of an optical signal is arranged on the first end face 21 and the second end face 22, and no waveguide end is arranged on the third end face 23 and the fourth end face 24.

On the first end surface 21, a waveguide end that functions as an incident portion 21-1 and an exit portion 21-3 is arranged. The incident portion 21-1 is coupled to the optical fiber 11, and the emitting portion 21-3 is coupled to the monitor PD5. A waveguide end that functions as an emission unit 22-1 to 22-8 is arranged on the second end surface 22. The emitting units 22-1 to 22-8 are coupled to the light receiving elements 6-1 to 6-8, respectively.

The optical circuit 2 according to the present embodiment leaks from the core to the clad to at least a part of the first end faces 21 to the fourth end faces 24 of the optical circuit 2 where the waveguide end is not arranged. A reflecting portion that reflects light toward the outside of the optical circuit 2 is provided. For example, the third end face 23 includes a reflecting portion 23-1, and the fourth end face 24 includes a reflecting portion 24-1. The reflecting portion may be a part of the third end face 23 and the fourth end face 24, but it is preferable that the reflecting portion is provided on the entire third end face 23 and the fourth end face 24. Further, the reflecting portion 21-2 may be provided on the portion of the first end face 21 where the incident portion or the exit portion is not arranged.

FIG. 2 shows an example of the reflecting portion in the AA'cross section. Reflecting portion 23-1, the inclination has been applied, using a refractive index difference of the optical circuit 2 and the air, reflecting the leaked light B ₁ leaked from the core of the optical circuit 2 to the cladding to the upper surface 25 of the optical circuit 2 Let me. The reflecting portion 23-1 is formed by inclining at a predetermined angle C with respect to a surface parallel to the surface on which the waveguide is arranged. The plane parallel to the plane on which the waveguide is arranged is, for example, the upper surface 25. When the leaked light B ₁ is incident on the reflecting portion 23-1, the leaked light B ₁ is reflected by the reflecting portion 23-1, and the reflected leaked light B ₂ is emitted from the upper surface 25 to the outside of the optical circuit 2. As a result, in the optical circuit 2, it is possible to prevent the optical circuit 2 from being coupled with the light propagation direction of the clad or the substrate again. In order to increase the reflectance of the reflective portion 23-1, it is preferable to apply a reflection treatment such as a coating to the reflective portion 23-1.

The predetermined angle C is set to an angle to be reflected according to the position of the reflecting portion. The predetermined angle C is preferably 45 °. The difference in the specific refractive index of the PLC is, for example, 1.5 when glass is used and 3.0 when Si is used. When the difference in specific refractive index is 1.5 or more, the critical angle becomes smaller than 45 °. Therefore, when the predetermined angle C is 45 °, the leaked light B ₁ can be reflected to the extent that the leaked light B _{1 is emitted from the upper surface 25.}

The method for manufacturing an optical circuit of the present embodiment includes a cutting step and a polishing step in this order.
In the cutting step, the optical circuit 2 is cut out from the wafer on which the plurality of optical circuits 2 are formed with a dicing saw.
In the polishing step, the end face of the cut-out optical circuit 2 is polished to form the reflecting portions 23-1 and 24-1. At this time, the end faces 23 and 24 of the optical circuit 2 are polished so that the end faces are inclined at a predetermined angle C with respect to the upper surface 25 or the lower surface 26. Examples of the polishing method include polishing by the CMP method. Thereby, the optical circuit 2 according to the present embodiment can be produced.

In the present embodiment, it is preferable that the inner wall surface 9A of the housing 9 on the optical path of _{the leaked light B 2} emitted from the optical circuit 2 is provided with the non-reflective portion 4 that absorbs the _{leaked light B 2.} For the non-reflective portion 4, for example, an antireflection coating can be exemplified. As a result, _{it is possible to prevent the leaked light B 2 from} being scattered in the housing 9.

FIG. 3 shows another form of installation of the non-reflective portion. The non-reflective portion 4 may be arranged on the optical path of the _{leaked light B 2 in} contact with the upper surface 25 of the optical circuit 2. As a result, even if the non-reflective portion 4 is not provided on the inner wall surface 9A of the housing 9 due to structural restrictions of the housing 9, or if parts are arranged between the optical circuit 2 and the housing 9, leakage occurs. It is possible to prevent the light B _{2 from} being scattered in the housing 9.

Although FIGS. 2 and 3 show an example in which the reflecting portion 23-1 reflects the leaked light B ₁ on the upper surface 25 of the optical circuit 2, the present embodiment is not limited to this. For example, the reflecting unit 23-1 may reflect the leaked light B ₁ on the lower surface 26 of the optical circuit 2. In this case, the third end surface 23 is tilted by a predetermined angle C with respect to the lower surface 26 to form the reflecting portion. The predetermined angle C is an angle formed by the lower surface 26 and the reflecting portion 23-1. Further, when the non-reflective portion 4 is provided, the non-reflective portion 4 is arranged in the housing 9 on the optical path of _{the leaked light B 2 emitted from the lower surface 26.} Alternatively, it is arranged on the lower surface 26 located on the optical path of the leaked light B _2.

Further, in the present embodiment, an example in which the optical module is a light receiving module is shown, but it can be applied to any optical module equipped with an optical circuit such as a transmission module.

As described above, since the optical circuit and the optical module of the present embodiment are provided with the reflecting portion for reflecting toward the outside of the optical circuit, scattering in the housing can be prevented, so that the light receiving sensitivity of the monitor PD deteriorates. Can be prevented. Further, by providing the non-reflective portion on the housing on the optical path of the leaked light or on the upper surface of the optical circuit, the scattering of the leaked light can be suppressed more effectively.

This disclosure can be applied to the information and communication industry.

11: Optical fiber 2: Optical circuit 21: First end face 21-1: Incident part 21-2: Reflection part 21-3: Exit part 22: Second end face 22-1, 22-2, 22-3, 22-4, 22-5, 22-6, 22-7, 22-8: Exit 23: Third end face 23-1: Reflection 24: Fourth end face 24-1: Reflect 25: Top surface 26 : Bottom surface 4: Non-reflective part 5: Monitor PD
6-1, 6-2, 6-3, 6-4, 6-5, 6-6, 6-7, 6-8: Light receiving elements 7-1, 7-2, 7-3, 7-4: Bias differential detectors 8-1, 8-2: Signal processing unit 9: Housing 9A: Inner wall surface of housing

Claims (3)

In an optical circuit in which a waveguide is formed in which the core is covered with a cladding.
Of the four surfaces sandwiched between the upper surface and the lower surface of the optical circuit and forming the outer circumference, the entire two surfaces on which the entrance / exit ends of the waveguide are not arranged are inclined, and the core to the said core. A reflective part that reflects the leaked light leaked to the clad toward the outside of the optical circuit.
Optical circuit with. A non-reflective portion which is arranged on the optical path of the leaked light reflected by the reflecting portion and emitted from the optical circuit and absorbs the leaked light emitted from the optical circuit is further provided.
The optical circuit according to claim 1. The optical circuit according to claim 1 and
The housing that covers the optical circuit and
A non-reflective portion of the inner wall surface of the housing, which is arranged on the optical path of the leaked light emitted from the optical circuit and absorbs the leaked light emitted from the optical circuit.
Optical module with.

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