How to Split an Ethernet Cable Without Losing Signal Strength?

I recently purchased a Samsung Blu-Ray player that connects to the internet for Netflix streaming. It is wifi enabled, but requires I buy an $80 USB wifi dongle before it will actually connect (link to dongle).

Luckily my new DVD player is right next to my internet setup, making a direct connection from my modem very convenient (I have one cable modem that connects to an Airport wireless router). Unfortunately my modem only has one outgoing Ethernet connection, so I am stuck having to manually switch the Ethernet cable between my DVD player and my router.

Can anyone tell me the best way for me to split my Ethernet cable coming from my modem so that it will connect to both my DVD player and my router? Preferably in a way the wont degrade the quality of the signal to either.