Technique for detecting noise on a data channel

• US 6,563,615 B2
• Filed: 12/07/2000
• Issued: 05/13/2003
• Est. Priority Date: 08/27/1997
• Status: Expired due to Term

• Current Assignee: Ciena Corporation
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Milton, David, Liu, Kexing, Valis, Tomas, Pigeon, Michel, Totti, Gino
• Primary Examiner(s): NEGASH, KINFE MICHAEL
• Application Number:
  US09/730,549
• Publication Number:
  US 20020126334A1
• Time in Patent Office: 887 Days
• Field of Search: 359/110, 359/124, 359/125, 359/158, 375/225, 375/227
• US Class Current: 398/1
• CPC Class Codes: H04J 14/0206 Express channels arrangements
• CPC Class Codes: H04J 14/0209 Multi-stage arrangements, e.g. by cascading multiplexers or demultiplexers
• CPC Class Codes: H04J 14/0212 using optical switches or wavelength selective switches [WSS]
• CPC Class Codes: H04J 14/0213 Groups of channels or wave bands arrangements
• CPC Class Codes: H04J 14/0226 Fixed carrier allocation, e.g. according to service
• CPC Class Codes: H04J 14/0227 Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
• CPC Class Codes: H04J 14/0241 Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths
• CPC Class Codes: H04J 14/0246 using one wavelength per ONU
• CPC Class Codes: H04J 14/025 using one wavelength per ONU, e.g. for transmissions from-ONU-to-OLT or from-ONU-to-ONU
• CPC Class Codes: H04J 14/028 WDM bus architectures
• CPC Class Codes: H04J 14/0282 WDM tree architectures
• CPC Class Codes: H04J 14/0283 WDM ring architectures
• CPC Class Codes: H04J 14/0284 WDM mesh architectures
• CPC Class Codes: H04J 14/0289 Optical multiplex section protection
• CPC Class Codes: H04J 14/0291 Shared protection at the optical multiplex section (1:1, n:m)
• CPC Class Codes: H04J 14/0298 with sub-carrier multiplexing [SCM]
• CPC Class Codes: H04Q 11/0062 Network aspects

Abstract

A communications network has a plurality of nodes interconnected by an optical transmission medium. The transmission medium is capable of a carrying a plurality of wavelengths organized into bands. A filter at each node for drops a band associated therewith and passively forwards other bands through the transmission medium. A device is provided at each node for adding a band to the transmission medium. Communication can be established directly between a pair of nodes in the network sharing a common band without the active intervention of any intervening node. This allows the network to be protocol independent. Also, the low losses incurred by the passive filters permit relatively long path lengths without optical amplification.

Claims

1. A method for determining whether a data channel is carrying valid traffic or noise, the method comprising:

receiving a digital signal on the data channel;

counting bits of the received digital signal for successive time intervals having substantially equal lengths; and

comparing the bit counts for the successive time intervals so as to determine if the bit counts vary by more than a predetermined amount over the successive time intervals.

2. The method as defined in claim 1, wherein:

the step of counting bits of the received digital signal comprises;

counting bits of the received digital signal over a first interval to generate a first bit count and capturing the first bit count in a first register; and

counting bits of the received digital signal over a second interval following the first interval to generate a second bit count and transferring the first bit count from the first register to a second register while capturing the second bit count in the first register; and

the step of comparing the bit counts for the successive time intervals comprises;

coupling the first bit count from the second register to a first input of a comparator; and

coupling the second bit count from first register to a second input of the comparator.

3. The method as defined in claim 2, wherein the step of counting bits of the received digital signal are performed by an edge counter.

4. The method as defined in claim 3, wherein the edge counter is reset and the registers are clocked by a clock signal having a period which comprises multiple bit periods of the received digital signal.

5. The method as defined in claim 1, further comprising the step of:

indicating that the data channel is carrying noise if the bit counts vary by more than the predetermined amount over the successive time intervals.

6. The method as defined in claim 1, further comprising the step of:

indicating that the data channel is carrying valid traffic if the bit counts vary by less than the predetermined amount over the successive time intervals.

7. An apparatus for determining whether a digital data channel is carrying valid traffic or noise, the apparatus comprising:

an input for receiving a digital signal on the data channel;

a bit counter for counting bits of the received digital signal for successive time intervals having substantially equal lengths; and

a comparator for comparing the bit counts for the successive time intervals so as to determine if the bit counts vary by more than a predetermined amount over the successive time intervals.

8. The apparatus as defined in claim 7, further comprising:

a first register having a clock input, a data input coupled to an output of the bit counter to receive bit counts from the bit counter when clocked, and an output coupled to a first input of the comparator;

a second register having a clock input, a data input coupled to an output of the first register to receive bit counts from the first register when clocked, and an output coupled to a second input of the comparator;

such that, when clocked together, the first and second registers are operable to;

couple a bit count for a current time interval from the bit counter into the first register and from the first register to the first input of the comparator, and

couple a bit count for a previous time interval from the first register into the second register and from the second register to the second input of the comparator, respectively.

9. The apparatus as defined in claim 8, further comprising:

a clock source operable to provide a clock signal having a period that comprises multiple bit periods of the received digital signal, the clock source being coupled to;

a reset input of the bit counter to reset the bit count;

the clock input of the first register; and

the clock input of the second register.

10. The apparatus as defined in claim 7, wherein the bit counter is an edge counter.

11. An apparatus for determining whether a data channel is carrying valid traffic or noise, the apparatus comprising:

an input for receiving a digital signal on the data channel;

means for counting bits of the received digital signal for successive time intervals having substantially equal lengths; and

means for comparing the bit counts for the successive time intervals so as to determine if the bit counts vary by more than a predetermined amount over the successive time intervals.

12. The apparatus as defined in claim 11, further comprising:

means for indicating that the data channel is carrying noise if the bit counts vary by more than the predetermined amount over the successive time intervals.

13. The apparatus as defined in claim 11, further comprising:

means for indicating that the data channel is carrying valid traffic if the bit counts vary by less than the predetermined amount over the successive time intervals.