  We report a wavelength division multiplexed time-bin entangled photon pair
source in telecom wavelength using a 10 {\mu}m radius Si ring resonator. This
compact resonator has two add ports and two drop ports. By pumping one add port
by a continuous laser, we demonstrate an efficient generation of two-wavelength
division multiplexed time-bin entangled photon pairs in the telecom C-band,
which come out of one drop port, and are then split into the signal and idler
photons via a wavelength filter. The resonator structure enhances four wave
mixing for pair generation. Moreover, we demonstrate the double-port pumping
where two counter propagating pump light are injected to generate entanglement
from the two drop ports simultaneously. We successfully observe the highly
entangled outputs from both two drop ports. Surprisingly, the count rate at
each drop port is even increased by twice as that of the single-port pumping.
Possible mechanisms of this observation are discussed. Our technique allows for
the efficient use of the Si ring resonator, and widens its functionality for
variety of applications.
