An optical splitter won't do you any good. The purpose of an optical splitter is to take the signal from a single source device (e.g. an Xbox) and split it so that it goes to multiple audio sink devices (e.g. your sound bar and another device that has an optical input). That isn't what you need as it doesn't sound like you have another device with an optical input. Note that your TV most likely does not have an optical input. Most likely, it only has an optical output. For that reason, it sounds like the device you are considering would be an optical switch, not an optical splitter. An optical switch allows you to connect the optical output of multiple source devices (e.g. an Xbox, TV, Playstation, satellite receiver, etc.) to a single optical input on your audio sink device (e.g. your sound bar).
However, when I looked at the online manual for your soundbar, I noticed that it has 3 inputs (one optical, one coaxial, and one mono RCA). That being the case, so long as you only have 2 source devices (e.g. your Xbox and your TV) that you want to connect to the sound bar, independently, using optical or coaxial cables, then you won't need a switch. Instead, you can use both the optical and coaxial inputs on the soundbar. This can be accomplished either by running optical from the TV to the soundbar and coaxial from the Xbox to the soundbar, or, by running optical from both the TV and the Xbox and using an optical-to-coaxial adaptor on the end of one of the cables where it plugs into the soundbar. Optical and coaxial digital audio cables are essentially equal in most use cases. Both carry the same signal and are capable of the same quality for a simple 6 foot run. The main advantage of optical over coaxial is that it is less prone to interference for extremely long runs (which you don't have). The main advantage of coaxial over optical is that it is more flexible and can be bent into tight loops where space is a concern. So, you would only need a switch if you have more than 2 source devices that you want to connect to the sound bar, independently.
P.S. If your TV is capable of passing 5.1 Dolby Digital audio from an external device, connected via HDMI, through its optical audio output then you are better off connecting all of your source devices (Xbox, Playstation, etc.) to the TV via HDMI and passing the audio through it. This way the TV can adjust the A/V lip sync as needed prior to sending the audio to your sound bar. If you run the audio straight from the Xbox to the soundbar then their could be a lip sync issue between the audio you hear from the sound bar and the video you see on the TV screen. You might be able to manually adjust the audio delay on your source devices and/or sound bar to compensate, but it's simpler to just let the TV do it automatically. The TV can only do this if you pass the audio through it.
