# US 10,371,897 B2 · Method and apparatus for providing multiport free-space WDM device using folded optical-path

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- Number: US 10,371,897 B2
- Document ID: US10371897B2
- Status: Granted
- Kind: B2
- Application number: 15/608,942
- Filed: 2017-05-30
- Published: 2017-09-14
- Granted: 2019-08-06
- Earliest claimed: 2014-12-31
- Assignees: OW Holding Inc.
- Applicants: Optiworks, Inc.
- Inventors: Xuefeng Yue
- Web page: https://patentgrep.com/patent/US10371897B2

## CPC

- G02B 6/29368: {Light guide comprising the filter, e.g. filter deposited on a fibre end (G02B6/29359 takes precedence)}
- G02B 6/29367: {Zigzag path within a transparent optical block, e.g. filter deposited on an etalon, glass plate, wedge acting as a stable spacer}
- G02B 6/29379: {characterised by the function or use of the complete device}
- G02B 6/2938: {for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM}
- G02B 6/327: {with angled interfaces to reduce reflections}
- G06V 40/1324: {by using geometrical optics, e.g. using prisms (G06V40/1312 takes precedence)}
- H04J 14/0305: {in end terminals}
- G02B 6/2937: {In line lens-filtering-lens devices, i.e. elements arranged along a line and mountable in a cylindrical package for compactness, e.g. 3- port device with GRIN lenses sandwiching a single filter operating at normal incidence in a tubular package}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G06V: IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
- H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S)

## Abstract

An optical wavelength-division multiplexing (“WDM”) device utilizing a mechanism of folded optical-path includes multiple collimators, optical filters, prism, and glass plate. The collimators are capable of collimating optical lights for facilitating free-space optical communication. The optical filters optically coupled with the collimators provide filtering functions to separate optical wavelengths in accordance with the configurations or characteristics of optical filters. The prism having an interface surface and two side surfaces is configured to direct or redirect optical beams based on the angle of incidence (“AOI”) of each optical beam received. The glass plate, in one embodiment, physically configured to be situated in parallel with the collimators is capable of providing free-space optical paths for facilitating separation of wavelengths.

## Claims

### Claim 1

An optical wavelength-division multiplexing (“WDM”) device, comprising:
an input collimator configured to receive an optical beam containing a plurality of wavelengths (“λn”) and facilitate the optical beam to travel through free-space;
a plurality of output collimators arranged in parallel to the input collimator;
an input prism placed at output of the input collimator and configured to have an angled surface for facilitating receiving and redirecting the optical beam;
a plurality of filters situated at inputs of the plurality of output collimators for facilitating demultiplexing the optical beam;
a prism having an interface surface and two side surfaces optically coupled to the input collimator, a first portion of the interface surface of the prism configured to interface with the plurality of output collimators, the two side surfaces of the prism configured to redirect light; and
a glass plate, having a reflective surface, coupled to a second portion of the interface surface of the prism and configured to facilitate free-space optical communication allowing light after redirected by the angled surface, traveling through at least a portion of the glass plate including the reflective surface for facilitating signal separation from the optical beam.

### Claim 2 (depends on 1)

The optical WDM device of claim 1, wherein the input prism an angled surface, is situated between the input collimator and the interface surface of the prism for facilitating entry point of the interface of the prism for the optical beam to enter from the input prism to the prism.

### Claim 3 (depends on 1)

The optical WDM device of claim 1, wherein a first output collimator of the plurality of output collimators has a lens end and a fiber end, and configured to receive a first output signal from the prism in accordance with the optical beam.

### Claim 4 (depends on 3)

The optical WDM device of claim 3, wherein a first optical filter of the plurality of filters, situated between the first output collimator and the prism, having an optical receiving surface which is situated at a predefined angle with respect to the interface surface of the prism for facilitating frequency separation.

### Claim 5 (depends on 4)

The optical WDM device of claim 4, wherein the first optical filter is configured to extract a first wavelength (“λ1”) from the plurality of wavelengths to form a first output light signal with λ1 and form a second optical beam with remaining wavelengths of the optical beam.

### Claim 6 (depends on 3)

The optical WDM device of claim 3,
wherein a second output collimator of the plurality of output collimators having a lens end and a fiber end, and configured to receive a second output signal from the prism in accordance with the optical beam; and
wherein a second optical filter of the plurality of filters placed between the second output collimator and the prism, and configured to separate the second output signal from the optical beam.

### Claim 7 (depends on 4)

The optical WDM device of claim 4, wherein the first optical filter is a thin film filter capable of directing one wavelength in a first direction and remaining wavelengths in a second direction.

### Claim 8 (depends on 1)

The optical WDM device of claim 1, wherein one side of the glass plate situated adjacent to the interface surface of the prism contains an angle which facilitates a function of angle of incidence for the optical beam.

### Claim 9 (depends on 1)

The optical WDM device of claim 1, wherein the glass plate is configured to reflect optical signals with a predefined reflective angle.

### Claim 10 (depends on 1)

The optical WDM device of claim 1, wherein the input collimator includes a fiber pigtail and a collimator lens wherein the fiber pigtail and the collimator lens are enclosed by a glass tube configured to transmit optical signals.

### Claim 11 (depends on 1)

A multiport free-space WDM system capable of facilitating optical communication comprising the optical WDM device of claim 1.

### Claim 12

A method of demultiplexing an optical light beam for a wavelength-division multiplexing (“WDM”) device, comprising:
guiding collimated input optical beam from an input collimator to an angled surface of a first prism and refracting the optical beam from the first prism toward a second prism with a predefined angle;
turning the optical beam in a first ninety (90) degree turn when the optical beam strikes a first side surface of the second prism to generate a 90-degree optical beam traveling toward a second surface of the second prism;
turning the 90-degree optical beam in a second ninety (90) degree turn when the 90-degree optical beam hits the second surface of the second prism to generate a first optical beam which travels approximately in an opposite direction of light traveling direction of the optical beam;
allowing the first optical beam to enter a glass plate with an incident angle generated by the angled surface for facilitating a signal separation process via a free space optical communication through the glass plate; and
guiding the first optical beam via a reflective surface of the glass plate toward a first output collimator of a plurality of output collimators.

### Claim 13 (depends on 12)

The method of claim 12, further comprising extracting a first wavelength (“λ1”) from the first optical beam to form a first light signal with λ1 when the first optical beam reaches to the first optical filter, and forming a second optical beam with remaining wavelengths of the first optical beam.

### Claim 14 (depends on 13)

The method of claim 13, further comprising redirecting the second optical beam from the first optical filter to the second prism passing through an interface surface of the second prism.

### Claim 15 (depends on 13)

The method of claim 13, further comprising allowing the first light signal to pass through the first optical filter reaching to a first collimator and forwarding the first light signal by the first collimator to a first port of the WDM device.

### Claim 16 (depends on 14)

The method of claim 14, further comprising redirecting the second optical beam from the second prism towards the glass plate permitting the second optical beam to pass through free-space facilitated by the glass plate.

### Claim 17 (depends on 14)

The method of claim 14, further comprising extracting a second wavelength (“λ2”) from the second optical beam when the second optical beam reaches to the second optical filter, and forming a third optical beam with remaining wavelengths of the second optical beam.

### Claim 18

An optical wavelength-division multiplexing (“WDM”) device utilizing folded optical-path, comprising:
a plurality of collimators including one input collimator and multiple output collimators capable of collimating optical lights for facilitating free-space optical communication;
an input prism having an angled surface coupled to the input collimator for guiding an optical beam;
a plurality of optical filters optically coupled with the plurality of output collimators and configured to filtering optical wavelengths in accordance with configurations of the plurality of optical filters;
a prism optically coupled with the plurality of optical filters and configured to have an interface surface and two side surfaces for redirecting optical light; and
a glass plate, having a reflective surface, optically coupled to the prism and physically configured to be situated in parallel with the plurality of collimators for facilitating free space optical paths for facilitating a process of signal separation from the optical light in response to redirected optical light via the angled surface and the reflective surface.

### Claim 19 (depends on 18)

The device of claim 18, wherein a portion of the interface surface is coated with anti-reflection and another portion of the interface surface is polished, wherein polished portion of the interface surface is coupled to a first surface of the glass plate.

### Claim 20 (depends on 18)

The device of claim 18, wherein the plurality of optical filters is aligned with anti-reflection portion of the interface surface with a predefined incident angle for facilitating wavelengths separation.

### Claim 21 (depends on 18)

The device of claim 18, wherein the plurality of collimators includes one input collimator and four output collimators.