Apparatus and method for performing line analysis of continuous data signals
View Patent ↗A method for performing an optical line analysis of continuous data signals transmitted in a passive optical network (PON). The method comprises determining, from an optical signal of the optical line, at least one of a phase early/late indicator based on a phase position of an input continuous data signal relative to sampling clock signals, a difference phase indicator based on an input phase control code, and a low frequency jitter indicator based on an input phase control code; computing a plurality of statistical measures regarding frequency and amplitude components of a jitter of the input continuous data signal, wherein the statistical measures are computed based on one of the phase early/late information indicator, the difference phase indicator, and the low frequency jitter indicator; and analyzing the plurality of statistical measures to detect optical failures in the PON and determining a root cause of each of the detected failures.
1. A clock and data recovery (CDR) circuit configured for detecting optical failures in a passive optical network (PON), comprising:
an over-sampler for over-sampling an input continuous data signal to generate a bit stream;
a phase estimation unit (PEU) for computing from the bit stream a phase position of the input continuous data signal relative to sampling clock signals;
a digital filter for computing a phase control code based on the phase position;
a statistical accumulation block (SAB) for performing jitter analysis using the phase position and the phase control code and providing a plurality of statistical measures of at least a jitter frequency component and a jitter amplitude component in different frequency ranges; and
a processor for analyzing aggregation of the statistical measures to detect optical failures in the PON and determining a root cause of each of the detected optical failures.
2. The CDR circuit of claim 1 , wherein a different frequency range for performing the jitter analysis is from a direct current (DC) frequency to a frequency that is an order of a frequency of the input continuous data signal.
3. The CDR circuit of claim 1 , wherein the detected optical failures and their root causes are reported to an operator of the PON to perform optical layer supervision.
4. The CDR circuit of claim 1 , wherein the processor is configured to detect an optical failure indicating that a reference clock of the over sampler is not within a specified locking range of the input continuous data signal, wherein the processor determines that the root cause of the optical failure is in any one of a faulty optical network unit (ONU) and a faulty optical line terminal (OLT) when same optical failure was detected for all ONUs in the PON.
5. The CDR circuit of claim 1 , wherein the processor is configured to detect an optical failure indicating a low frequency measured jitter for the input continuous data signal, wherein the root cause of the optical failure is any one of noisy transmission by an optical line terminal (OLT) and an unstable power source of an optical network unit (ONU), wherein the CDR circuit is installed in the ONU.
6. The CDR circuit of claim 1 , wherein the processor is configured to detect an optical failure indicating that a measured jitter of the input continuous data signal is within an acoustic band, wherein the root cause of the optical failure is acoustic interferences on an optical fiber of the PON.
7. The CDR circuit of claim 1 , wherein the SAB further comprises:
a phase position processor for computing a phase early/late indicator based on the phase position;
a phase control code processor for computing a difference phase indicator based on the phase control code;
a frequency extractor for computing a low frequency jitter indicator based on the phase control code, wherein the low frequency jitter indicator is a binary representation of a frequency deviation between a reference clock and a clock of the input continuous data signal; and
a statistical calculator for computing the plurality of statistical measures regarding the jitter of the frequency and amplitude components of the input continuous data signal, wherein the statistical measures are computed based on at least one of the phase early/late indicator, the difference phase indicator, and the low frequency jitter indicator.
8. The CDR circuit of claim 7 , further comprising:
a down sampler for down sampling one of the phase early/late indicator, the difference phase indicator, and the low frequency jitter indicator to a frequency working point of a filter; and
a filter for filtering the down sampled signal to a predefined frequency window in which the input continuous data signal is to be analyzed, wherein the output of the filter is fed to the statistical calculator.
9. The CDR circuit of claim 1 , wherein the plurality of statistical measures include at least one of: a maximum value, a minimum value, an absolute value, an average value, and a standard deviation value.
10. The CDR circuit of claim 8 , wherein the SAB is further configured to measure a transferred jitter of a signal transmitted by an optical network unit (ONU) based on at least the phase control code.
11. The CDR circuit of claim 1 , further comprising:
a reference clock; and
a phase interpolator for generating the sampling clock signals at an oscillating frequency of the reference clock.
12. The CDR circuit of claim 11 , wherein the oscillating frequency of the reference clock is generated by an oscillator.
13. The CDR circuit of claim 11 , wherein the oscillating frequency of the reference clock is generated by a recovered clock phase locked loop device.
14. The CDR circuit of claim 11 , wherein each of the sampling clock signals are phase shifted with respect to a preceding clock signal.
15. The CDR circuit of claim 7 , wherein the statistical calculator computes the plurality of statistical measures regarding the jitter of the frequency and amplitude components of the input continuous data signal in real-time.
16. The CDR circuit of claim 7 , wherein the frequency extractor comprises a statistical block for computing at least one of minimum, maximum, absolute, and average values of the frequency deviation, wherein the output of the statistical block is fed to the processor.
17. The CDR circuit of claim 7 , wherein the SAB further comprises:
a multiplexer for selecting output of one of the phase position processor, the phase control code processor, and the frequency extractor to be input to a down sampler.
18. The CDR circuit of claim 8 , wherein the filter is an infinite impulse response filter.
19. The CDR circuit of claim 8 , wherein the filter is a finite impulse response filter.
20. The CDR circuit of claim 1 , wherein the PON carries data of a high-speed serial bus, wherein the high-speed serial bus comprises at least one of a Serial ATA (SATA) bus, a Peripheral Component Interconnect express (PCIe) bus, a Universal Serial Bus, a Hypertransport bus, and an Infiniband bus.