In the dynamics of optical systems one commonly needs to cope with the problem of coexisting deterministic and stochastic components. The separation of these components is an important although difficult task. Often the time scales at which determinism and noise dominate the system's dynamics differ. In this letter we propose to use information-theory-derived quantifiers, more precisely permutation entropy and statistical complexity, to distinguish between the two behaviors. Based on experiments of a paradigmatic optoelectronic oscillator we demonstrate that the time scales at which deterministic or noisy behavior dominate can be identified. Supporting numerical simulations prove the accuracy of this identification. c 2011 Optical Society of America OCIS codes: 140.1540, 190.3100, 250.5960, 000.5490. Delayed coupling phenomena play an important role in optical systems, including semiconductor lasers with feedback [1], delay-coupled lasers [2], and optoelectronic oscillators [3]. In particular, the latter have proven to be practical benchmark systems to study delay dynamics [3,4]. Moreover, these oscillators have turned out to be versatile systems for novel applications such as chaos communications [5] or generation of ultra-high spectral purity microwaves [6]. The main dynamical features of this test-bed system are well documented and characterized, both from the theoretical and the experimental point of view [7]. Experimental realizations of the optoelectronic oscillator are usually affected by an unpredictable stochastic component. In particular, when the dynamical system is driven into the hyperchaotic regime, it can be hard to distinguish between the deterministic chaotic dynamics and the stochastic component when they coexist. To distinguish between these two components we propose, in this letter, to use quantifiers derived from information theory. In particular, permutation entropy and statistical complexity [8] are good candidates for this task. They have already shown to be successful in identifying the internal structures of time series originated from delay systems [9,10].To compute these quantifiers, we analyze the time series of the system's dynamics and from them construct a probability distribution of their amplitudes. We choose the Bandt and Pompe method due to its simplicity and effectiveness [11]. Band and Pompe consider the order of neighboring values, by comparing their amplitude values, rather than partitioning the amplitude into different levels. This avoids amplitude threshold sensitivity dependences. The probability distribution of the generated ordinal pattern for a given time series can be established once an embedding dimension D and an embedding delay time τ are chosen. The embedding dimension D refers to the number of symbols that forms the ordinal pattern. The embedding delay τ is the time separation between symbols which is directly related to the sampling time of the time series (see refs. [9-11] for a detailed derivation and description of the quantifiers). Fig. 1. The optoel...