I make a device that converts the proprietary Fanuc "serial pulse coder" format to quadrature. Fanuc makes some VERY nice encoders in this series. You can often get them on eBay. They do have encoders that go over 1 million counts/rev. The ones with an A in the model number have absolute data that allows them to be used as an absolute encoder, but the high resolution data may not be accurate unless a backup battery is provided. So, an (alpha) I 64 would have 65536 counts/rev, but no absolute data, the (alpha)A64 would have the absolute data.
Feel free to ask if you need more info. The position can be interrogated at up to 8 KHz.
Jon