IrDA hardware is tuned for low quality LEDs and Photodiodes that have as far as several meters to traverse. (Aka: more noise issues).

To go Gbps bandwidth, you need higher quality everything. You probably have a better job starting from Ethernet SFP kinds of fiber optics rather than the cheap IrDA hardware.

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You probably will have great difficulty reviving 4Mbps fast IrDA, let alone 1000Mbps protocols that were only ever a spec sheet in practice....