One fiber is for transmitting, the other for receiving, but it doesn’t matter which does which — “transmit/receive” is going to be different from each switch’s point of view anyway, isn’t it? All you need to do is make sure you have one switch’s TX connected to the other’s RX and vice versa. You can’t damage anything by plugging it in wrong, it just won’t work, so go ahead and try it — you have a 50/50 chance of getting it right the first time!
<i>You should also take care about the fact that you may change fibers on patch cable or in patch panel to make cross-connection. The used light can also make problems if you have different wavelenths on Tx and Rx side. Just be aware of that possible problem. Good luck! </i>