In digital communication systems, the bit rate is the number of bits transmitted per second. It is typically measured in bits per second (bps). The bit sequence length is the number of bits in a given sequence. The number of samples per bit is the number of samples taken per bit during the process of analog-to-digital conversion (ADC) or digital-to-analog conversion (DAC).

The time window is the duration of time over which samples are taken and analyzed. It is typically measured in seconds. The number of samples is the total number of samples taken over the time window. The sample rate is the number of samples taken per second. It is typically measured in samples per second (SPS).

In OptiSystem, you can use the following formula to calculate the time window:

Time window = (bit sequence length) / (bit rate)

To calculate the number of samples, you can use the following formula:

Number of samples = (time window) x (sample rate)

To calculate the sample rate, you can use the following formula:

Sample rate = (number of samples) / (time window)

For example, if you have a bit rate of 1.25e-009, a bit sequence length of 1000 bits, and several samples per bit of 8, you can calculate the time window as follows:

Time window = (1000 bits) / (1.25e-009 bits/s) = 0.8 seconds

You can then calculate the number of samples as follows:

Number of samples = (0.8 seconds) x (8 samples/bit) = 6.4e+003 samples

And you can calculate the sample rate as follows:

Sample rate = (6.4e+003 samples) / (0.8 seconds) = 8 samples/s

I hope this helps! Let me know if you have any more questions.