Optical phase diversity receiver for coherent optical communication using periodic and identical chirped grating surfaces

Patent metadata

Field	Value
Publication number	US-9720177-B2
Application number	US-201615170626-A
Country	US
Kind code	B2
Filing date	Jun 1, 2016
Priority date	Jun 24, 2015
Publication date	Aug 1, 2017
Grant date	Aug 1, 2017

Abstract

An optical phase diversity receiver may include: a diffraction grating including grating surfaces; a first input waveguide to which a first optical signal is inputted; a second input waveguide to which a second optical signal is inputted; and a slab waveguide including an input terminal optically coupled with the first and second input waveguides, and an output terminal provided at a position at which optical signals reflected by the diffraction grating reach the slab waveguide. Every determined number of grating surfaces are chirped in an identical manner. The slab waveguide is configured to guide the first and the second optical signals to the diffraction grating and guide the optical signals reflected by the diffraction grating to the output terminal. The grating surfaces are configured such that each of the optical signals reflected by the diffraction grating is divided into the predetermined number by optical power distribution.

First claim

What is claimed is:

1. An optical phase diversity receiver for coherent optical communication, comprising:
a diffraction grating including a plurality of grating surfaces, wherein every predetermined number of grating surfaces are chirped in an identical manner;
a first input waveguide to which a first optical signal is inputted;
a second input waveguide to which a second optical signal is inputted; and
a slab waveguide including an input terminal optically coupled with the first and second input waveguides, and an output terminal provided at a position at which optical signals reflected by the diffraction grating reach the slab waveguide, the slab waveguide being configured to guide the first and second optical signals received on the input terminal to the diffraction grating and guide the optical signals reflected by the diffraction grating to the output terminal,
wherein the plurality of grating surfaces are configured such that each of the optical signals reflected by the diffraction grating is divided into the predetermined number by optical power distribution.

2. The optical phase diversity receiver according to claim 1 ,
wherein the second input waveguide is disposed at a predetermined angle relative to the first input waveguide such that an angle at which the first optical signal is incident on the slab waveguide and an angle at which the second optical signal is incident on the slab waveguide differ from each other, and
wherein the predetermined angle is determined such that a reflection angle of the first optical signal reflected by the diffraction grating and a reflection angle of the second optical signal reflected by the diffraction grating are identical with each other.

3. The optical phase diversity receiver according to claim 2 ,
wherein the first input waveguide and the second input waveguide are disposed such that a diffraction order of the first optical signal and a diffraction order of the second optical signal differ from each other on the input terminal of the slab waveguide.

4. The optical phase diversity receiver according to claim 3 , further comprising:
first to eighth output waveguides optically coupled to the output terminal,
wherein the first to fourth output waveguides are respectively and optically coupled at positions at which TE (transverse electric) components of the optical signals reflected by the diffraction grating reach the output terminal, and
wherein the fifth to eighth output waveguides are respectively and optically coupled at positions at which TM (transverse magnetic) components of the optical signals reflected by the diffraction grating reach the output terminal.

5. The optical phase diversity receiver according to claim 4 ,
wherein each of the plurality of grating surfaces is a grating surface by which an incident optical signal is reflected according to equation 1,
wherein the equation 1 is

d
⁡

(

sin
⁡

(
α
)

+

sin
⁡

(

θ
m

)

)

=

mλ

n
eff

,

and
d denotes an interval of one grating surface of the plurality of grating surfaces,
α denotes an incident angle of the incident optical signal,
θ m denotes a reflection angle depending on a diffraction order of the incident optical signal,
m denotes a diffraction order of the incident optical signal,
λ denotes a wavelength of the incident optical signal, and
n eff denotes an effective refractive index.

6. The optical phase diversity receiver according to claim 4 ,
wherein the output terminal is disposed such that optical signals that are respectively incident on the first to fourth output waveguides have different phases, and optical signals that are respectively incident on the fifth to eighth output waveguides have different phases.

7. The optical phase diversity receiver according to claim 6 ,
wherein the first output waveguide is optically coupled with the output terminal at a point at which an optical signal having an I (0°) component focuses on the output terminal,
wherein the second output waveguide is optically coupled with the output terminal at a point at which an optical signal having an I-bar (180°) component focuses on the output terminal,
wherein the third output waveguide is optically coupled with the output terminal at a point at which an optical signal having a Q (90°) component focuses on the output terminal, and
wherein the fourth output waveguide is optically coupled with the output terminal at a point at which an optical signal having a Q-bar (270°) component focuses on the output terminal.

8. The optical phase diversity receiver according to claim 6 ,
wherein the fifth output waveguide is optically coupled with the output terminal at a point at which an optical signal having an I (0°) component focuses on the output terminal,
wherein the sixth output waveguide is optically coupled with the output terminal at a point at which an optical signal having an I-bar (180°) component focuses on the output terminal,
wherein the seventh output waveguide is optically coupled with the output terminal at a point at which an optical signal having a Q (90°) component focuses on the output terminal, and
wherein the eighth output waveguide is optically coupled with the output terminal at a point at which an optical signal having a Q-bar (270°) component focuses on the output terminal.

9. The optical phase diversity receiver according to claim 4 , further comprising:
an optical detector optically coupled with the first to eighth output waveguides at a side opposite to the output terminal and configured to receive an optical signal and convert the received optical signal into an electrical signal.

10. The optical phase diversity receiver according to claim 1 ,
wherein the plurality of grating surfaces are configured such that positions or reflection angles of every predetermined number of the grating surfaces are chirped in an identical manner.

11. The optical phase diversity receiver according to claim 10 ,
wherein the predetermined number of grating surfaces are defined as one period,
wherein the plurality of grating surfaces include a first grating surface and a second grating surface that are repeatedly arranged each period, and
wherein the first grating surface and the second grating surface differ in length of a path of an optical signal based on a center wavelength.

12. The optical phase diversity receiver according to claim 11 ,
wherein a length of a path of an optical signal formed by the first grating surface is shorter or longer than a length of a path of an optical signal formed by the second grating surface by a predetermined multiple based on the center wavele

Assignees

• Electronics & Telecommunications Res Inst

Inventors

• An Shin Mo
• Kwon Oh Kee

Classifications

• G02B6/29308

  Diffractive element having focusing properties, e.g. curved gratings (Rowland circle spectrometers G01J3/20) · CPC title

• G02B6/2931 Primary

  Diffractive element operating in reflection · CPC title

• G02B6/2938

  for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM · CPC title

• G02B6/29307

  components assembled in or forming a solid transparent unitary block, e.g. for facilitating component alignment · CPC title

• G02B6/2706

  as bulk elements, i.e. free space arrangements external to a light guide, e.g. polarising beam splitters · CPC title