Method and system for characterizing optical receivers by mathematical derivation
View Patent ↗The present invention describes the method and system for characterizing optical receivers based on the measured impulse response and by applying linear system theory. In a first embodiment, the impulse response of an optical receiver is obtained. Convolving the impulse response with band-limited input pulses (modeled with straight-line edge pulses), a receiver output pulse can then be determined. From this pulse, an associated eye diagram can be mathematically derived and the maximum ISI can be estimated. In a second embodiment, for a given input pulse stream with a specified amount of noise, the impulse response-generated eye diagram is used to estimate the bit error rate (BER) that the receiver would yield.
1. A method for characterizing a digital optical receiver, comprising:
creating an output pulse waveform by convolving a receiver impulse response and an input pulse;
generating an eye diagram by repeatedly overlaying the output pulse waveform every bit period.
2. The method of claim 1 , further comprising:
prior to the creating step, obtaining a bit stream for transmission, thereby generating an input sequence.
3. The method of claim 2 , further comprising:
prior to the obtaining step, estimating a transmitted pulse input waveform for a receiver, thereby generating pulses used to obtain the bit stream.
4. The method of claim 3 , further comprising:
prior to the estimating step, measuring the receiver impulse response from the receiver.
5. The method of claim 2 , wherein the bit stream is obtained as follows:
Σ n a n *P ( t−n*T )
where P is a pulse shape, T is a pre-determined bit period, and an is the input sequence.
6. The method of claim 1 , wherein the output pulse waveform is obtained as follows:
Σ n a n *X ( t−n*T+d )
where T is a pre-determined bit period, an is an input sequence, d is the delay in the receiver, and X( ) is a function for creating a pulse stream.
7. The method of claim 1 , further comprising:
after the generating step, estimating a worst case bit rate error (BER) and an amount of noise present in the receiver from an amount of eye closure in the eye diagram.
8. A computer-implemented method, comprising:
(a) creating a first output pulse waveform by convolving a first receiver impulse response and a first input pulse;
(b) generating an eye diagram from the first output pulse waveform at a first bit period;
(c) creating a second output pulse waveform by convolving a second receiver impulse response and a second input pulse; and
(d) generating the eye diagram by overlaying the first output pulse waveform with the second pulse waveform at a second bit period.
9. The method of claim 8 , further comprising:
repeating steps (c) and (d) for a subsequent bit period.