How to design Power Line communication with line transceivers?
This answer was produced before the OP explicitly revealed that he was proposing to use amplitude modulation rather than try and push raw data onto the power line.

is there any other configuration for this system that works with a
smaller inductor?

An effective powerline communication system (whether it's DC or AC power) should adopt a data modulation scheme to ensure that the required spectrum at the receiver is as band-limited as it can be. This, in its basic form usually means FSK (frequency shift keying) and band-limiting with a band-pass filter before transmitting to the line. The receiver would also use a similar band-pass filter before amplifying and demodulating/detecting the data. In other words, make your spectral occupancy as small as possible given the FSK frequencies and your data bandwidth: -

Picture from here. I've added red blocks where band pass filtering is needed to avoid load-power interference whilst simultaneously allowing the communication signals to effectively interface with the power line. In many respects it boils-down to a radio system using a &quot;wire&quot;.
It looks like you are trying to feed digital data directly to the line using an RS485/RS422 transceiver and this is going to produce problems in that low frequencies are going to be significantly attenuated by the DC pass inductor. Also, the bandwidth of the transmitted data will be naturally large and this means that any receiver has to have an open door for distortions produced by the load when drawing an irregular or cyclic DC current.
Regarding that inductor, you can make it AC resonant at the FSK frequencies and this will act as a band-limited block to those frequencies and this, in turn allows a smaller inductance value because, parallel tuning it with a capacitor will give a high blocking impedance to the FSK.
Do yourself a favour and use an FSK regime. What data rate are you contemplating by the way?