1. What is the maximum number of bits that can be generated by the ADC being produced now?
2. What is the maximum number of input bits that can be processed by a microprocessor?
3. Specific questions about Optical Time Domain Reflectometer (OTDR). Anyone know how the microprocessor inside the OTDR convert the input bits from ADC to the data on the graph (dB vs km), shown by OTDR?
Stevan, There are three major ADC types that are relevant to your question. You have to pick three parameters to start : a) sampling rate, b) sampling depth (bits) c) power consumption.
Three ADC types are:
1) SAR (Successive Approximation Register)- type: You will get fairly low power consumption (uW is possible, but, generally, low-mW), Max. 12 bit depth, rarely I see 14b, and the sampling rates are 200 KSPS (kilo-samples-per-second), or, sometimes up to 1 MSPS, if you are willing to reduce the depth to 10b etc ... Example: MICROCHIP MCP3201.
2) DELTA SIGMA: These ADC's achieve a lower noise by OVERSAMPLING. So, the usable sampling rate to you is in the high KSPS range. However, you get significantly higher bit depths, and the power consumption is very reasonable. I have seen 24b ADCs. Example: Analog Devices AD7718
3) FLASH: This is where you increase power consumption a lot ! But, the sampling rate increases too. There are even GBPS ADC's. TI has a very rich set of offerings:
http://www.ti.com/lsds/ti/data-converters/analog-to-digital-converter-products.page
I will answer the other question later
As per your second question: I assume that, you are asking about EMBEDDED processors. A 16b processor (e.g., dsPIC series from Microchip) can process data samples 16b at a time. A 32b processor can process them 32b at a time (e.g., PIC32MX series from Microchip).
However, don't forget, most 8 bit processors have a 16bit data type, and they use two registers to describe a 16 bit number. For example, if you use a 12 bit ADC as an input to a 8 bit processor, this is perfectly fine. But, you will be using more MCU instructions to process it, since it will map to TWO natural data types (i.e., byte) inside.
As per the third question, I don't know if your OTDR has a software development kit, I.,e., does it allow you to SEE the samples ? IF so, there will be API functions to allow you to observe the data samples, In the end, your OTDR is using one of the MCU's I mentioned above ...
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