All-optical clock recovery is essential operation in optical communication systems [1, 2]. Single and dual channel all-optical clock recovery from 40 Gbit/s return to zero on off keying (RZ-OOK) signal has been demonstrated using a silicon microring resonator (MRRs) assisted with a semiconductor optical amplifier (SOA) [1]. The main reason for SOA implementation after clock extraction is to minimize the impact from patterning effects [2]. In this paper we numerically demonstrate the properties of all-optical clock recovery with cascaded single ring MRRs [3] in four channel from 40 Gbit/s 50% RZ-OOK optical signal using OptSim simulation software. Channels are spaced 0.16 THz apart. MRR filter cascadability is used to minimalize patterning effects for recovered optical clock.