OPTICAL MODULE
An optical module comprising: a submount provided on a CAN stem; light-emitting device and a light-receiving device; a CAN cap or package; and an optical multiplexer/demultiplexer having a wavelength selective filter on a substrate that has transmissivity to passing light and a mirror, where an extending direction of the optical multiplexer/demultiplexer is fixed in the CAN cap or the package being tilted by an angle θ (θ≠2Nπ, N=0, 1, 2, . . . ) in a two-dimensional cross section with respect to one surface of an optical device mounting board, outgoing light from the light-emitting device passes through the wavelength selective filter and the substrate and enters an optical fiber outside the cap, and outgoing light from the optical fiber enters the optical multiplexer/demultiplexer and is reflected by the wavelength selective filter and further reflected by the mirror, and then exits the optical multiplexer/demultiplexer to enter the light-receiving device.
1 . An optical module comprising:
a submount provided on a CAN stem;
at least a first light-emitting device and a first light-receiving device provided on one surface of the submount and using a wavelength different to each other;
a CAN cap or a CAN package fixed on the stem and having a hole on the top for taking in and out light; and
an optical multiplexer/demultiplexer in a parallel-plate shape and having a first wavelength selective filter on one surface of a first substrate that has transmissivity to passing light, and a mirror on another surface facing the one surface of the first substrate, wherein
an extending direction of the optical multiplexer/demultiplexer is fixed in the CAN cap or the package being tilted by an angle θ (where θ≠2Nπ, N=0, 1, 2, . . . ) in a two-dimensional cross section with respect to a one surface of an optical device mounting board,
outgoing light from the first light-emitting device passes through the first wavelength selective filter and the first substrate and enters an optical fiber outside the cap, and
outgoing light from the optical fiber enters the optical multiplexer/demultiplexer and is reflected by the first wavelength selective filter and further reflected by the mirror, and then exits the optical multiplexer/demultiplexer to enter the first light-receiving device.
2 . The optical module according to claim 1 , wherein
the submount comprises a second light-receiving device,
the outgoing light from the optical fiber is wavelength-multiplexed light including light having wavelengths λ 2 and λ 3 (where λ 2 ≠λ 3 ),
the outgoing light from the optical fiber enters the optical multiplexer/demultiplexer and is reflected by the first wavelength selective filter and further reflected by the mirror, and then the light having the wavelength λ 2 passes through a second wavelength selective filter provided on the one surface of the first substrate and exits the optical multiplexer/demultiplexer to enter the first light-receiving device, and
the light having the wavelength λ 3 is reflected by the second wavelength selective mirror and further reflected by the mirror, and then exits the optical multiplexer/demultiplexer to enter the second light-receiving device.
3 . The optical module according to claim 1 , wherein
an edge portion of the optical multiplexer/demultiplexer is fixed inside the cap.
4 . The optical module according to claim 1 , wherein
in the process where the outgoing light from the optical fiber is reflected by the first wavelength selective filter and reflected again by the mirror arranged to face the first wavelength selective filter, the mirror has transmissive/reflective characteristics to transmit light within a pass band of the first wavelength selective filter.
5 . The optical module according to claim 1 , wherein
the mirror is a wavelength selective filter which is same with the first wavelength selective filter positioned before the mirror on the light path.
6 . The optical module according to claim 1 , wherein
a substrate member of the first substrate is amorphous glass, sapphire crystal, crystal quartz, or silicon.
7 . The optical module according to claim 1 , wherein
the package including the stem and the cap is a metal CAN package, and concave and convex portions are provided to an inner wall part of the cap to fix the first substrate at the angle θ.
8 . The optical module according to claim 1 , wherein
the first light-emitting device is provided so as to emit light perpendicular to one surface of the optical device mounting board where the optical devices are mounted on the submount.
9 . The optical module according to claim 8 , wherein
a lens is provided to a light-emission plane of the optical devices.
10 . The optical module according to claim 1 , wherein
an order of alignment of the optical devices mounted in one line on the submount is in ascending order or descending order of the wavelength used by respective devices.
11 . The optical module according to claim 1 , wherein
the outgoing light from the optical fiber or the first light-emitting device enters to the one surface of the first substrate of the optical multiplexer/demultiplexer at an incident angle θ 1 (where θ 1 ≠90°) and exits at an emission angle θ 2 (where θ 2 ≠90°), and light having different wavelengths is demultiplexed or multiplexed in a process of multiple reflections of the incident light between a wavelength selective filter array and a mirror array, and
a relationship of a distance between a filter surface and a mirror surface d, an inclination to a horizontal surface of the filter surface θ 1 , an external refractive index n 1 , and a refractive index of a chassis n 2 satisfies
z= 2 d ·tan θ 2 ·cos θ 1 ≧100 (μm).
12 . The optical module according to claim 1 , wherein
the outgoing light from the optical fiber or the first light-emitting device enters to the one surface of the first substrate of the optical multiplexer/demultiplexer at an incident angle θ 1 (where θ 1 ≠90°) and exits at an emission angle θ 2 (where θ 2 #90°), and light having different wavelengths is demultiplexed or multiplexed in a process of multiple reflections of the incident light between a wavelength selective filter array and a mirror array, and
when taking a distance between a filter surface and a mirror surface is d, a distance x from an optical axis of the outgoing light of the first light-emitting device to an optical axis of the incident light from the optical fiber reaching onto the one surface satisfies
x=d ·sin(θ 1 −θ 2 )/cos θ 2 (μm).
13 . The optical module according to claim 1 , wherein
each filter configuring a filter array of the optical multiplexer/demultiplexer is an edge filter which has a property of transmitting light having a wavelength larger or equal to or smaller than or equal to a desired demultiplexing wavelength within a range of all wavelengths used by the optical devices and a property of reflecting light other than that, and an order of alignment of the edge filters on the filter array is in ascending order or descending order of the demultiplexing wavelengths.