At first glance, it seems unnecessary to clearly define the the strong mode coupling and weak mode coupling in few mode fiber? However, the concepts of strong mode coupling in different publishing works seems have different meaning. In [], the author define the strong mode coupling by using the mode coupling coefficient. The larger of the mode coupling coefficient means the stronger of mode coupling. This definition is intuitionistic and has been widely used for analysis the linearly mode coupling for two mode situation. However, for 3mode or more number of modes, one of mode coupling coefficient is obviously not enough to define the strong mode coupling. In [], the authors define the strong mode coupling according to the length of the so-called correlation length. However, is the correlation length parameter enough for defining the strong mode coupling?
Mode coupling can be either weak or strong. Generally, depend on the length of a system. on the other hand, mode coupling can be define as either strong or weak depend on the constructive or destructive of power interference between modes.
Thanks for your answer! if there is a mode coupling event in the link and all of the modes were involved in this events, and the strength of each mode coupling coefficients are large enough, the overall transmission matrix of the FMF may show strong mode coupling even with short interaction length .On the other hand, if partial of modes involved in these random coupling events in the link, these modes will not couple with each other even after long haul transmission
Hey Liang,
Your references don't show up for me. I would be interested in looking at them. Thank you for sharing.
Hi Kerrianne Harrington:
Thanks for your answer! several references define the strong mode coupling according to the so-called correlation length, such as
[1]K.-P. Ho and J. M. Kahn, "Statistics of Group Delays in Multimode Fiber with Strong Mode Coupling", J. of Lightwave Technol., vol. 29, no. 21, pp. 3119-3128, November 1, 2011.
[2]S. �. Arik, D. Askarov and J. M. Kahn, "Effect of Mode Coupling on Signal Processing Complexity in Mode-Division Multiplexing", J. of Lightwave Technol. vol. 31, no. 13, pp. 423-431, February 1, 2013.
In this model, they separate the FMF or MMF as multi-sections according to the correlation length, the more number of sections means the stronger of mode coupling! but what is the correlation length? In the reference
[3] Y.Xiao, R.J.Essiambre, M.Desgroseilliers, A.M.Tulino, R.Ryf, S.Mumtaz, G.P.Agrawal, “Theory of intermodal four-wave mixing with random linear mode coupling in few-mode fibers.,” Opti.Express, 22(26) 32039-32059. (2014).
the correlation length is defined as the length that all of the mode coupling coefficient can keep as constants. If the correlation length defined in [1][2] is same as [3], I think only one of correlation length parameter is not enough to define strong mode coupling. Several references about two-mode transmission define the strong mode coupling according to the mode coupling coefficient, such as
[4]D.Rafique, S. Sygletos and A.D.Ellis,"Impact of power allocation strategies in long-haul few-mode fiber transmission systems" opti.Express 21(9) 10801-10809
the larger of mode coupling coefficient means the stronger of mode coupling. However, for more number of modes, one parameter seems not enough to describe the strong mode coupling
Hello, Can anyone here know the limit for the numerical value of the distance of core separation of a dual core fiber for the weakly coupled regime? I do agree with the fact that the strong/weak coupled mode regime depend on the the core separation distance in case of dual core. Thanks in advance.
This work may answer your question
1. K.Saitoh, S.Matsuo. Multicore fiber technology. Journal of Lightwave Technology, 2016,34(1):55-66
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