  In this paper we do a detailed numerical investigation of the fault-tolerant
threshold for optical cluster-state quantum computation. Our noise model allows
both photon loss and depolarizing noise, as a general proxy for all types of
local noise other than photon loss noise. We obtain a threshold region of
allowed pairs of values for the two types of noise. Roughly speaking, our
results show that scalable optical quantum computing is possible for photon
loss probabilities less than 0.003, and for depolarization probabilities less
than 0.0001. Our fault-tolerant protocol involves a number of innovations,
including a method for syndrome extraction known as telecorrection, whereby
repeated syndrome measurements are guaranteed to agree. This paper is an
extended version of [Dawson et al., Phys. Rev. Lett. 96, 020501].
