Methods and systems for detecting optical link performance of an optical link in a hybrid fiber coaxial path

• US 6,498,663 B1
• Filed: 09/24/1999
• Issued: 12/24/2002
• Est. Priority Date: 09/24/1999
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Scientific-Atlanta Incorporated (Cisco Systems, Inc.)
• Inventors: Labiche, Michael J., Farhan, Forrest M.
• Primary Examiner(s): Pascal, Leslie
• Assistant Examiner(s): Phan, Hanh
• Application Number:
  US09/406,281
• Time in Patent Office: 1,187 Days
• Field of Search: 359/110, 359/158, 359/180, 359/125, 359/154, 359/135, 370/503, 370/509, 370/514
• US Class Current: 398/27
• CPC Class Codes: H04B 10/0795 Performance monitoring; Measurement of transmission parameters
• CPC Class Codes: H04B 10/07953 Monitoring or measuring OSNR, BER or Q
• CPC Class Codes: H04L 1/242 by comparing a transmitted test signal with a locally generated replica

Abstract

A broadband network, such as a cable television system, includes a synchronous code generator that converts an analog signal into a digital signal and inserts a synchronous code in the digital signal. The synchronous code generator is in communication with an optical link, which transmits the digital signal. An optical performance monitor receives the digital signal from the optical link and determines performance of the optical link based on errors in the synchronous code. The optical link performance monitor includes an error detector, which detects errors in the synchronous code, and, in response thereto, signals a counter of the error. The counter accumulates the errors detected by the error detector for a period of time. A processor, which is in communication with the counter, determines the optical performance of the optical link based upon the number of errors accumulated by the counter. A user interface displays the results of the processor.

Claims

1. A method for detecting optical link performance of an optical link in a hybrid fiber coax path, comprising:

converting an analog signal to a digital signal for transmission over an optical link in a hybrid fiber coax path, wherein the digital signal contains a synchronous code;

transmitting the digital signal including the synchronous code along the optical link to a receiver;

monitoring for errors in the synchronous code at the receiver, wherein the step of monitoring comprises the steps of;

detecting errors in the synchronous code, and in response,

storing a count of the errors in the synchronous code; and

determining optical performance based upon the errors detected in the synchronous code.

2. The method of claim 1, wherein the step of determining optical performance comprises the step of determining a bit error rate of the digital signal based upon the errors detected in the synchronous code.

3. The method of claim 2, further comprising the step of determining a noise to power ratio measurement from the bit error rate.

4. The method of claim 1, wherein the step of determining optical performance comprises the step of determining a bit error rate of the digital signal based upon errors accumulated in the counter.

5. The method of claim 4, further comprising the step of determining a noise to power ratio measurement from the bit error rate.

6. A system for detecting optical link performance of an optical link in a in a hybrid fiber coax path, comprising:

a synchronous code generator that generates a synchronous code that is inserted into a digital signal;

an optical link in communication with the synchronous code generator, wherein the optical link transmits the digital signal, and

an optical performance monitor that receives the digital signal from the optical link and determines performance of the optical link based on errors in the synchronous code,

wherein the optical performance monitor comprises;

an error detector in communication with the optical link, wherein the error detector detects errors in the synchronous code, and in response thereto generates error signals;

a counter in communication with the error detector, wherein the counter accumulates the error signals received from the error detector for a period of time; and

a processor in communication with the counter, wherein the processor determines the optical performance of the optical link based upon the number of errors accumulated by the counter.

7. The system of claim 6, wherein the synchronous code comprises a plurality of predetermined characters.

8. The system of claim 6, wherein the counter comprises a first register for accumulating the error signals from the error detector.

9. The system of claim 8, further comprising a second register in communication with the first register, wherein the second register transmits data received from the first register to the processor.

10. The system of claim 6, wherein the counter comprises:

a first register for accumulating the errors in the synchronous code;

a second register in communication with the first register, wherein the second register stores data from the first register for transmission to the processor;

a multiplexer in communication with the second register, wherein the multiplexer transmits the data stored in the second register from the second register to the processor; and

a serial peripheral interface in communication with the second register, wherein the serial peripheral interface transmits the data stored in the second register from the second register to the processor.

11. The system of claim 6, wherein the processor determines a bit error rate of the digital signal based upon errors accumulated by the counters.

12. A system for detecting optical link performance of an optical link in a hybrid fiber coax path, comprising:

means for converting an analog signal to a digital signal for transmission over an optical link in a hybrid fiber coax path, wherein the digital signal contains a synchronous code;

means for transmitting the digital signal including the synchronous code along the optical link to a receiver;

means for monitoring optical performance of the digital signal in the optical link, wherein the means for monitoring optical performance of the digital signal in the optical link comprises;

means for detecting errors in the synchronous code, and in response,

means for counting the detected errors in the synchronous code, wherein the counting means accumulates detected errors, and

means for determining optical performance based upon errors detected in the synchronous code.

13. The system of claim 12, wherein the means for determining optical performance comprises means for determining a bit error rate of the digital signal based upon errors detected in the synchronous code.

14. The system of claim 13, further comprising means for determining a noise to power ratio measurement from the bit error rate.

15. The system of claim 12, wherein the means for determining optical performance comprises means for determining a bit error rate of the digital signal based upon errors accumulated in the means for counting.

16. The system of claim 15, further comprising means for determining a noise to power ratio measurement from the bit error rate.