an hdmi interconnect arrangement is presented that performs a pulse - amplitude modulation conversion of the tmds audio / video signals in order to simultaneously transmit all three channels over a single optical fiber . the set of three audio / video tmds channels is applied as an input to a pam - 8 optical modulator , which functions to encode the set of three channels onto an optically - modulated output signal . the modulated optical signal is thereafter coupled into an optical fiber within an active hdmi cable and transmitted to an hdmi receiver . the tmds clk signal is not included in this conversion into the optical domain , but remains as a separate electrical signal to be transmitted along a copper signal path within the active hdmi cable .