Is it possible to interface this optical mouse sensor with the arduino mega? Datasheet: Datasheet
Yes but being a 3V3 device you will need signal level converters.
May I know where is the SDIO pin?
12458:
May I know where is the SDIO pin?
Pins are shown in the datasheet (note the circular mark near pin 1).
There is no "SDIO" pin on the Arduino MEGA. The SPI hardware uses separate output and input pins. You will probably need to use software SPI (shiftIn() and shiftOut()) and switch the data pin of your choice from pinMode(OUTPUT) to pinMode(INPUT) as needed. You'll need the protocol manual to figure out how to send commands and receive data.