Patent Application
20160216446
This application claims priority from Korean Patent Application No. 10-2015-0013768, filed on Jan. 28, 2015, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety.
1. Field
The following description relates to an optical communication, and more particularly, to an apparatus for monitoring an optical signal in an optical waveguide-based optical device.
2. Description of the Related Art
In an optical communication system, an optical transceiver module that plays a key role in opto-electrical and electro-optical conversion is expected to be compact, low-cost, and low power consumption by monolithic integration in which active and passive optical devices are fabricated on the same process platform. For the monolithic integration, an optical waveguide-based structure for monitoring an optical signal is required.
U.S. Pat. No. 7,305,185, assigned to Enablence, which is a vendor for optical devices and modules, discloses a configuration for optical channel monitoring. In this document, in order to monitor channel wavelength of an optical signal, an optical tap is added to an optical waveguide, which splits the optical signal into a desired portion of light that goes to a demultiplexer providing optical outputs. The split optical signals are converted into electric signals by an external multi-channel photodiode, which causes an increase in the overall size of the module.
U.S. Pat. No. 7,957,438, assigned to JDS Uniphase, discloses a configuration for monitoring light. An optical signal launched from a light source to a fiber is mostly transmitted through a core of the fiber, and the remaining portion is transmitted through the cladding of the fiber. In this configuration, a photodiode is placed on the top of the cladding of the fiber and monitors the optical signal. Such a configuration increases the structural complexity in the packaging of the photodiode and the overall size of the package.
The following description relates to an apparatus for monitoring an optical signal based on an optical waveguide, which is advantageous for monolithic integration.
In one general aspect, there is provided An apparatus for monitoring an optical signal, including: a light absorbing layer formed on an optical waveguide consisting of a core layer and upper and lower cladding layers; and a photodiode including electrodes arranged on both the optical waveguide and the light absorbing layer.
In another general aspect, there is provided an apparatus for monitoring an optical signal, including: a light absorbing layer formed on an optical waveguide consisting of a core layer and upper and lower cladding layers; and a photodiode including electrodes arranged on the light absorbing layer.
Other features and aspects will be apparent from the following detailed description, the drawings, and the claims.
Fig
Throughout the drawings and the detailed description, unless otherwise described, the same drawing reference numerals will be understood to refer to the same elements, features, and structures. The relative size and depiction of these elements may be exaggerated for clarity, illustration, and convenience.
The following description is provided to assist the reader in gaining a comprehensive understanding of the methods, apparatuses, and/or systems described herein. Accordingly, various changes, modifications, and equivalents of the methods, apparatuses, and/or systems described herein will be suggested to those of ordinary skill in the art. Also, descriptions of well-known functions and constructions may be omitted for increased clarity and conciseness.
The present invention relates to an apparatus for monitoring an optical signal, which is integrated onto an optical waveguide, and provides mainly two exemplary embodiments thereof according to the positions at which electrodes of a photodiode of the apparatus for detecting optical signals are formed.
According to a first exemplary embodiment, an apparatus for monitoring an optical signal has electrodes of a photodiode formed on both an optical waveguide and a light absorbing layer.
According to a second exemplary embodiment, an apparatus for monitoring an optical signal has all electrodes of a photodiode formed only on a light absorbing layer.
The photodiode of the apparatus converts an optical signal detected from the optical waveguide into an electrical signal.
Each exemplary embodiment will be described in detail with reference to the accompanying drawings below.
Referring to
The optical waveguide 10 is a target for monitoring an optical signal and consists of a core layer 11, an upper and lower cladding layers 12.
The light absorbing layer 20-1 is formed on the core layer 11 of the optical waveguide 10 and absorbs an optical signal propagating through the core layer 11.
The photodiode 30-1 includes an electrode 31-1 formed on the light absorbing layer 20-1 and electrodes 32-1 formed on the core layer 11 of the optical waveguide. Each electrode 31-1 and 32-1 may be formed by the ion doping technique (n-type doping and p-type doping). Although the positive and negative electrodes 31-1 and 32-1 of the photodiode 30-1 are shown as a rectangle in the drawings, aspects of the present disclosure are not limited thereto, such that the electrodes of the photodiode 30-1 may be formed in various shapes, such as a circle, as well as a rectangle. In addition, various embodiments may be available for the shape of electrodes of the photodiode 30-1 relative to a direction along which light travels.
Referring to
Referring to
In addition, various embodiments may be available for the shape of electrodes of the photodiode 30-2 of
Referring to
Cross-sectional views of the apparatus taken long line A-A′ of
The optical signal traveling in the optical waveguide is evanescent wave-coupled to the light absorbing layers (refractive index=n1) 21 with a higher refractive index than that of the core layer (refractive index=n2) 11-1. The relationship of the refractive indices of the core layer 11-1 (n2), which is a medium, and the light absorbing layer 21 (n1) is expressed mathematically as: “n1>n2”.
The amount of optical signal coupled to the light absorbing layer (refractive index=n1) 21 may vary according to the length of the photodiode (length of evanescent-wave coupling, LmPD) of the optical waveguide with a fixed width, a ratio between the thickness (HWG) of the core layer 11-1 of the optical waveguide and the thickness HmPD of the light absorbing layer 21, and quantum efficiency of a working wavelength of the light absorbing layer 21. Specifically, as the length (LmPD) of the photodiode increases, as the light absorbing layer 21 is thicker than the core layer 11-1, or as the quantum efficiency of the light absorbing layer 21 increases, the amount of optical signal launched into the photodiode increases.
As an example of a photodiode for general communications, a silicon photonics-based photodiode is provided, which consists of germanium layer (refractive index: n1−4.3), as a light absorbing layer, being formed on an optical waveguide (core layer: silicon (Si, refractive index: n2−3.5: cladding layer: SiO1, refractive index: n3−4.3). Here, the refractive index represents a value at a wavelength of 1.5 μm.
Although the apparatus shown in
Referring to
Referring to
In addition, although not illustrated in drawings, the positive and negative electrodes of the photodiode 30-3 and 30-4 may be arranged parallel or perpendicular to a direction 1 in which light travels.
Furthermore, the cross-sectional structures of the apparatus taken along line A-A′ may be the same as those shown in
According to the exemplary embodiments, the photodiode that is a photodetector is arranged on the optical waveguide and monitors an optical signal, so that the size of an optical integrated circuit capable of monitoring an optical signal can be remarkably reduced.
A number of examples have been described above. Nevertheless, it will be understood that various modifications may be made. For example, suitable results may be achieved if the described techniques are performed in a different order and/or if components in a described system, architecture, device, or circuit are combined in a different manner and/or replaced or supplemented by other components or their equivalents. Accordingly, other implementations are within the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2015-0013768 | Jan 2015 | KR | national |
