Signal detector for GPON optical line terminal
A circuit detects a digital pattern with a first counter having an input receiving a digital pattern, and an output providing an output signal after detecting a first number of pulses during a first time period. A latch has an input coupled to the output of the first counter for latching the output signal of the first counter. A second counter has an input receiving the digital pattern, and an output providing an output signal after detecting a second number of pulses during a second time period. A logic gate has a first input coupled the output of the first counter, and a second input coupled to the output of the second counter, and an output coupled to the input of the latch. An amplitude detection circuit has an input coupled for receiving the digital pattern and an output coupled to the input of the first counter.
1. A signal detection circuit, comprising:
an amplitude detection circuit comprising an input coupled for receiving a signal;
a first counter including an input coupled to an output of the amplitude detection circuit, wherein the first counter provides an output signal with a first logic state after counting a first predetermined number of pulses in the signal during a first time period and otherwise provides the output signal with a second logic state; and
a latch having an input coupled to an output of the first counter for latching the output signal of the first counter.
2. The signal detection circuit of claim 1 , further including a second counter coupled for receiving the signal, wherein the second counter provides an output signal with a first logic state after counting a second predetermined number of pulses of the signal during a second time period.
3. The signal detection circuit of claim 2 , further including a logic gate comprising a first input coupled to the output of the first counter, and a second input coupled to an output of the second counter, and an output coupled to the input of the latch.
4. The signal detection circuit of claim 2 , wherein a portion of the first time period overlaps a portion of the second time period.
5. The signal detection circuit of claim 2 , wherein the first time period is consecutive with the second time period.
6. A circuit for detecting a digital pattern of an optical signal from an optical receiving circuit, comprising:
a first counter including an input coupled for receiving the digital pattern of the optical signal, and an output providing an output signal with a first logic state after detecting a first predetermined number of pulses of the digital pattern of the optical signal during a first time period and otherwise provides the output signal with a second logic state;
a second counter including an input coupled for receiving the digital pattern of the optical signal, and an output providing an output signal with a first logic state after detecting a second predetermined number of pulses of the digital pattern of the optical signal during a second time period and otherwise provides the output signal with a second logic state;
a logic gate comprising a first input coupled to the output of the first counter, and a second input coupled to the output of the second counter; and
a latch having an input coupled to an output of the logic gate for latching an output signal of the logic gate.
7. The circuit of claim 6 , wherein a portion of the first time period overlaps a portion of the second time period.
8. The circuit of claim 6 , wherein the first time period is consecutive with the second time period.
9. The circuit of claim 6 , further including an amplitude detection circuit comprising an input coupled for receiving the digital pattern of the optical signal and an output coupled to the input of the first counter.
10. The circuit of claim 6 , wherein the digital pattern of the optical signal is a preamble of a burst mode optical transmission.
11. A method of making a semiconductor device including a circuit for detecting a digital pattern of an optical signal from an optical receiving circuit, comprising the steps of:
providing a first counter including an input coupled for receiving a digital pattern of the optical signal, and an output providing an output signal with a first logic state after detecting a first predetermined number of pulses of the digital pattern of the optical signal during a first time period and otherwise provides the output signal with a second logic state; and
providing a latch having an input coupled to the output of the first counter for latching the output signal of the first counter.
12. The method of claim 11 , further including the step of providing a second counter including an input coupled for receiving the digital pattern of the optical signal, and an output providing an output signal with a first logic state after detecting a second predetermined number of pulses of the digital pattern of the optical signal during a second time period.
13. The method of claim 12 , further including the step of providing a logic gate comprising a first input coupled to the output of the first counter, and a second input coupled to the output of the second counter, and an output coupled to the input of the latch.
14. The method of claim 12 , wherein a portion of the first time period overlaps a portion of the second time period.
15. The method of claim 12 , wherein the first time period is consecutive with the second time period.
16. The method of claim 11 , further including the step of providing an amplitude detection circuit comprising an input coupled for receiving the digital pattern of the optical signal and an output coupled to the input of the first counter.
17. The method of claim 11 , wherein the digital pattern of the optical signal is a preamble of a burst mode optical transmission.
18. A circuit for detecting a digital pattern of an optical signal from an optical receiving circuit, comprising:
a first counter including an input coupled for receiving a digital pattern of the optical signal, and an output providing an output signal with a first logic state after detecting a first predetermined number of pulses of the digital pattern of the optical signal during a first time period and otherwise provides the output signal with a second logic state; and
a latch having an input coupled to the output of the first counter for latching the output signal of the first counter.
19. The circuit of claim 18 , further including a second counter including an input coupled for receiving the digital pattern of the optical signal, and an output providing an output signal with a first logic state after detecting a second predetermined number of pulses of the digital pattern of the optical signal during a second time period.
20. The circuit of claim 19 , further including a logic gate comprising a first input coupled to the output of the first counter, and a second input coupled to the output of the second counter, and an output coupled to the input of the latch.
21. The circuit of claim 19 , wherein a portion of the first time period overlaps a portion of the second time period.
22. The circuit of claim 19 , wherein the first time period is consecutive with the second time period.
23. The circuit of claim 18 , further including an amplitude detection circuit comprising an input coupled for receiving the digital pattern of the optical signal and an output coupled to the input of the first counter.