[calamari4065]

The universe is likely infinite. The part we can observe is finite, and growing smaller.

Outside of our observable universe is probably just more universe. We're stuck in a bubble within that universe due to the speed of light and cosmic expansion. The expansion of the universe is accelerating and that expansion continually pushes more of the universe outside of our local bubble. Relative to our reference point, some parts of the universe are moving away faster than the speed of light.

Supposing you had some sort of mechanism to travel across the entire universe, when you get to what we on Earth would see as the 'edge' of the observable universe, you could see past the boundary to another section of the universe as big as this one. If you could communicate back to earth, you'd effectively increase the size of our observable universe by half.

But while we're still trapped by the speed of light, we can never see beyond the edge of the universe. An edge which grows closer and closer, faster and faster with every passing second.

No matter how big your sensor is, you can't detect photons that don't exist. Once an object passes beyond the boundary of our observable universe, it effectively ceases to exist for us. No photon from that object will ever reach us again.