# US 8,571,415 B1 · Regenerators placement mechanism for wavelength switched optical networks

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- Number: US 8,571,415 B1
- Document ID: US8571415B1
- Status: Granted
- Kind: B1
- Application number: 10/097,901
- Filed: 2002-03-13
- Granted: 2013-10-29
- Earliest claimed: 2001-07-19
- Assignees: Alcatel Lucent
- Applicants: Douglas Clayton Rider; James Craig Slezak; Anthony Vernon Walker Smith
- Inventors: Douglas Clayton Rider; James Craig Slezak; Anthony Vernon Walker Smith
- Web page: https://patentgrep.com/patent/US8571415B1

## CPC

- H04Q 11/0005: {Switch and router aspects}
- H04J 14/0227: {Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation}
- H04J 14/0246: {using one wavelength per ONU}
- H04J 14/0257: {Wavelength assignment algorithms}
- H04J 14/0267: {Optical signaling or routing}
- H04J 14/0268: {Restoration of optical paths, e.g. p-cycles}
- H04J 14/0269: {using tables for routing}
- H04J 14/0283: {WDM ring architectures}
- H04J 14/0284: {WDM mesh architectures}
- H04J 14/0221: {Power control, e.g. to keep the total optical power constant}
- H04Q: SELECTING (switches, relays, selectors H01H; wireless communication networks H04W)
- 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

The method of placing regenerators along a trail connecting a source network node with a destination network node of an automatically switched optical network first identifies N tentative regeneration sites and n+1 optical paths along the trail. Wavelengths are assigned to each optical path; and the performance of the trail is assessed based on regenerator placement data and wavelength assignment data. The data identifying this regenerator path, namely regenerator placement data, the wavelength assignment data and the performance parameter of the trail are stored in a list, if the performance parameter is over a threshold. Selection of the tentative sites is revised whenever the initial placement fails due to a reach problem, a wavelength-blocking problem or a path quality problem. If the time for revising the initial placement, or the cost of a regenerator path is unacceptable, the regenerator path is abandoned and a further placement is initiated. Next, a further regenerator placement is attempted for the same trail using n+1 regenerators, and the further regenerator path is stored in the list, etc. Still further, regenerator placement is attempted for another trail, and so on, until a specified number of regenerator paths are stored in the list.

## Claims

### Claim 1

In an automatically switched optical network, a method of placing regenerators along a trail connecting a source network node with a destination network node, comprising:
(a) selecting n tentative regeneration sites S(i) connected by n+1 optical paths along said trail by calculating an average distance dave for said trail based on a maximum wavelength reach and the length of said trail, determining n based on the calculated dave and identifying said n tentative regeneration sites based on dave;
(b) selecting a path wavelength for each said optical path; and
(c) determining a performance parameter of said trail based on regenerator placement data obtained at (a) and wavelength assignment data obtained at (b).

### Claim 2 (depends on 1)

A method as claimed in claim 1, further comprising (d) storing said regenerator placement data, said wavelength assignment data and said performance parameter of said trail in a list, if said performance parameter is over a threshold.

### Claim 3 (depends on 2)

A method as claimed in claim 2, further comprising (e) repeating steps (a) to (d) for a further trail for obtaining a further trail data, and ordering said trail data and said further trail data in said list according to said performance parameter.

### Claim 4 (depends on 1)

A method as claimed in claim 1, further comprising revising selection of said tentative regeneration sites and of said path wavelengths if steps (a)-(c) fail.

### Claim 5 (depends on 4)

A method as claimed in claim 4, wherein said step of revising is performed based on time and cost estimates.

### Claim 6 (depends on 1)

A method as claimed in claim 1, further comprising:
(a4) determining if a regenerator can be placed at a respective tentative regeneration site; and:
(a5) if yes, placing said regenerator at said respective tentative regeneration site and repeating steps (a4) and (a5) until all regenerators are placed at said respective tentative regeneration sites.

### Claim 7 (depends on 6)

A method as claimed in claim 6, further comprising,
(a6) re-placing a regenerator REGEN(i) at a network node adjacent to said respective tentative regeneration site S(i) if said regenerator REGEN(i) cannot be placed at said tentative regeneration site S(i) due to one of a reach estimate problem and a constraint applicable to said trail; and
(a7) re-placing all regenerators downstream from said regenerator REGEN(i).

### Claim 8 (depends on 7)

A method as claimed in claim 7, further comprising placing an additional regenerator along said trail if steps (a6)-(a7) fail.

### Claim 9 (depends on 1)

A method as claimed in claim 1, wherein step (b) comprises:
(b1) determining if a continuous wavelength is available on each said optical path OP(i); and
if a continuous wavelength is not available on an optical path OP(i),
(b2) identifying a problem node along said OP(i) and re-placing a regenerator REGEN(i) tentatively placed at the output of said optical path OP(i) at said problem node; and
(b3) re-placing all regenerators downstream from said regenerator REGEN(i).

### Claim 10 (depends on 9)

A method as claimed in claim 9, further comprising, placing an additional regenerator along said trail and re-placing all regenerators downstream from said regenerator if step (b3) fails.

### Claim 11 (depends on 1)

A method as claimed in claim 1, wherein step (c) comprises:
for each optical path of said trail, importing network topology data from a topology database and importing network performance data from a performance database;
calculating a path performance parameter based on said network topology data and network performance data; and
calculating said performance parameter for said trail based on all said path performance parameters.

### Claim 12 (depends on 11)

A method as claimed in claim 11 further comprising, revising selection of said tentative regeneration sites to optimize said performance parameter of each optical path of said trail.

### Claim 13 (depends on 11)

A method as claimed in claim 11 further comprising changing the respective path wavelength of a certain path OP(i) with a better performing wavelength, if available, when said performance parameter of said OP(i) is under a threshold.

### Claim 14 (depends on 13)

A method as claimed in claim 13, wherein said performance parameter of said optical path is the Q factor estimated for said optical path.

### Claim 15 (depends on 11)

A method as claimed in claim 11, further comprising re-placing a regenerator REGEN(1) at a tentative regenerator site at the output of a certain optical path OP(i) at a network node upstream from said tentative regenerator site, and re-placing all regenerators downstream from said regenerator REGEN(i), when the performance parameter of said optical path OP(i) is under a threshold.

### Claim 16 (depends on 11)

A method as claimed in claim 11, further comprising, placing an additional regenerator along a certain optical path OP(i) and re-placing all regenerators downstream from said additional regenerator, when the performance parameter of said optical path OP(i) is under a threshold.

### Claim 17 (depends on 1)

A method as claimed in claim 1, wherein said performance parameter is one of the cost of said trail, the Q factor estimated for said trail, and bath the cost and the Q factor.

### Claim 18 (depends on 1)

A method as claimed in claim 1, wherein a first version of said performance parameter is calculated for all optical paths of said trail which have a light loading, and a second version of said performance parameter is calculated for all optical paths of said trail that have a heavy loading.