Multi-stage optical DWDM channel group interleaver

• US 6,546,166 B1
• Filed: 11/05/2001
• Issued: 04/08/2003
• Est. Priority Date: 11/05/2001
• Status: Expired due to Fees

• Current Assignee: Alliance Fiber Optic Products Incorporated (Corning Incorporated)
• Original Assignee: Alliance Fiber Optic Products Incorporated (Corning Incorporated)
• Inventors: Tsay, Wei-Shin, Liu, Yuqiao
• Primary Examiner(s): Palmer, Phan T. H.
• Application Number:
  US10/011,584
• Time in Patent Office: 519 Days
• Field of Search: 385/24, 385/37, 385/16, 385/14, 385/15, 385/31, 385/42, 385/46, 385/33, 385/34, 359/115, 359/124, 359/130, 359/127
• US Class Current: 385/24
• CPC Class Codes: G02B 6/29364 Cascading by a light guide path between filters or filtering operations, e.g. fibre interconnected single filter modules
• CPC Class Codes: G02B 6/2938 for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM
• CPC Class Codes: G02B 6/29386 Interleaving or deinterleaving, i.e. separating or mixing subsets of optical signals, e.g. combining even and odd channels into a single optical signal

Abstract

An optical fiber structure for demultiplexing/multiplexing includes a coupler which splits an incoming signal with multiple channels into two substantially identical signals that are respectively processed to separate the closely located successive channel groups for further demultiplexing or multiplexing. The spectrum characteristics to process the two identical signals are so chosen that the channel distortion and/or transmission loss are minimized. In particular, multiple stages of splitter filters are used to shorten the transmission path a channel signal has to pass through. As a result, signal distortion and/or transmission loss are minimized and the channel groups are interleaved by a single channel group.

Claims

1. A fiber optical device comprising:

an optical splitting device receiving a multiplexed signal carrying channel groups numbered odd or even, each including a number of individual channels and the splitting device outputting two substantially identical signals of the multiplexed signal;

a first stage of filters configured to be first and second subgroups of the filters, each of the subgroups of the filters coupled to the splitting device and receiving one of the two identical signals, wherein respective frequency responses of the first and second subgroups are so designed that eventually the even numbered channel groups are respectively separated from the odd numbered channel groups; and

a second stage of filters configured to be a number of subgroups of the filters, each of the subgroups in the second stage coupled to one of the filters in the first stage and independently outputting one of the channel groups.

2. The fiber optical device of claim 1, wherein the respective frequency responses for the first subgroups and the second subgroups in the first stage are so arranged that each of the filters therein outputs a number of the channel groups, wherein the output channel groups are respectively separated by one of the channel groups.

3. The fiber optical device of claim 2, wherein each of the respective frequency responses has a cut-off frequency transition falling into the one of the channel groups that separates the output channel groups so that the output channel groups are not distorted.

4. The fiber optical device of claim 3, wherein each of the filters in the second stage has a band filtering frequency response that drops out all except for one of the output channel groups.

5. The fiber optical device of claim 4, wherein the band filtering frequency response is so designed that the one of the output channel groups that is not dropped out is not distorted at all.

6. The fiber optical device of claim 1, wherein the filters of the first subgroup in the first stage are successively coupled to each other and the filters of the second subgroup in the first stage are successively coupled to each other.

7. The fiber optical device of claim 1, wherein the optical splitting device is a coupler.

8. A fiber optical device comprising:

a coupler receiving a multiplexed signal including channel groups numbered even or odd, and the coupler outputting two identical signals of the multiplexed signal; and

two groups of filters, each receiving one of the two identical signals, each of the two groups including at least two stages of filters, the filters in each of the stages being configured in subgroups, the filters in each of the subgroups being successively coupled to each other, wherein a frequency response for each of the subgroups in either one of the two groups is so designed that, in one of the two identical signals, all of the odd numbered channels groups are subsequently separated from the even numbered channels, in another one of the two identical signals, all of the even numbered channels groups are subsequently separated from the odd numbered channels.

9. The fiber optical device of claim 8, wherein the respective frequency response for each of the subgroups in either one of the two groups has band pass characteristics to allow a portion of the channel groups received at the each of the subgroups to pass through while reflecting the rest of the channel groups received to an adjacent subgroup in the subgroups at one of the at least two stages.

10. The fiber optical device of claim 9, wherein the respective frequency response for each of the subgroups in either one of the two groups has transitions falling into two neighboring channel groups so that the portion of the channel groups passing through the each of the subgroups are not distorted.

11. A method for demultiplexing/multiplexing a composite signal including multiple channel groups numbered even or odd, the method comprising:

generating two identical signals from the composite signal;

coupling respectively the identical signals to a first stage of filters configured to be first and second groups of the filters, each of the groups of the filters receiving one of the two identical signals and outputting a number of channel group clusters, each of the channel group clusters including an odd number of the channel groups and every two of the channel group clusters being separated by one of the channel groups;

coupling the channel group clusters to subsequent stages of filters to further separating the channel group till the channel groups in each of the channel group clusters is interleaved by one of the channel groups in the each of the channel group clusters; and

wherein the one of the channel groups that separates the two of the channel group clusters and the one of the channel groups in the each of the channel group clusters that interleaves the channel groups in the each of the channel group clusters are an either odd or even numbered channel group.

12. The method of claim 11, wherein a frequency response of either the first and second groups of the filters is so designed that the channel group clusters are transmitted through without being distorted while two neighboring single channel groups are severally distorted.

13. The method of claim 11, wherein each of the two neighboring single channel groups that are severally distorted is the one of the channel groups separating every two of the channel group clusters.

14. The method of claim 11, wherein each of the subsequent stages of filters has a number of filters, and wherein the number of filters and the subsequent stages of filters are so designed that each of the channel groups travels at least number of the filters so that a distortion and transmission/insertion loss of the each of the channel groups is minimized.

15. A method for demultiplexing/multiplexing a composite signal including multiple channel groups numbered even or odd, the method comprising:

determining a transmission/insertion loss C for a coupler that is to separate the composite signal into two substantially identical signals, each respectively processed in two separate branches comprising multiple stages of filters;

determining from the filters that each reflection has an insertion loss of reflection ILR while each transmission has an insertion loss of transmission ILT;

minimizing a valuation of LOSS_max, wherein LOSS_max=ILR*(M1−

2)*(M2−

2)*, . . . , (ML−

2)*(X−

1)+C+ILT*(L+1), if ILT≧

ILR;

or LOSS_max=ILR*(M1−

1)*(M2−

1)*, . . . , (ML−

1)*(X−

1)+C+ILT, if ILT<

ILR; and

wherein N is a total number of individual channels in the composite signal and equal to or approximately close to 2*M1*M2* . . . ML*X, and wherein there are M1 subgroups in each branch at a first stage, each of the M1 subgroups is further divided into M2 subgroups at the second stage, and till to last ML subgroups at the Lth stage that has X channel groups.

16. The method of claim 15 further comprising outputting from the last ML subgroups even channel groups in one channel group cluster and odd channel groups in another channel group cluster.