text: From the expression above, we ﬁnd that the pumping statis- 
  tic can inﬂuence the linewidth. For regular injection (*p*= 1), 
  the linewidth is the narrowest, while for Poissonian injection 
  (*p*= 0), the linewidth is the broadest. But even for regular 
  injection, the linewidth is larger than the case of one cavity. 
  That means the mechanism of separated-ﬁeld does not play 
  the role in reducing the linewidth as in the conventional opti- 
  cal Ramsey method, which is counter-intuitive. However, the 
  separated ﬁelds are indispensable for any phase detection like 
  atom interferometry. The details about the method of active 
  atom interferometry will appear elsewhere. 
  
  1 
  *I*0 
  (δϕ2)ω =  (δ*Y*2)ω. 
  
  1  1 
  
  κ/2, as in the recently 
  τ− 
  In the region γ*ab*≪ 
  proposed active optical clock [15] with atomic beam. The 
  phase quadrature component of the ﬁeld ﬂuctuations can be 
  expressed as 
  
  *T*− 
  ≪  ≪ 
  
  *g*2 
  4(κ/2 + γ*ab*)2 { 
  4γ*ab*˜*Nass*