In computer networking circles, bandwidth means how much data a channel can carry, so the more the merrier. It’s usually measured in a multiple of bits per second (bps)—Kbps, Mbps, Gbps, and so on.
With fiber-optic cabling bandwidth is usually expressed in terms of MHz-km. So, a cable rated at 400 MHz-km could carry 400 Mbps of data a distance of 1 kilometer, 200 Mbps of data a distance of 2 kilometers, 100 Mbps of data a distance of 4 kilometers, etc.