The transmitter sends LPI in place of idle to indicate that the link can go to sleep.
After sending LPI for a period (Ts = time to sleep), the transmitter can stop signaling altogether so that the link becomes quiescent.
for a period
Periodically, the transmitter sends some signals so that the link does not remain quiescent for too long without a refresh. Finally, when the transmitter wishes to resume the fully functional link, it sends normal idle signals. After a pre-determined time (Tw = time to wake) the link is active and data can be sent [13].