Fig. 2 Average value the assertiveness index in the classification of 11 databases varying the number of neighbours when KFCV is applied to 10 KFCV iterations.
Fig. 4 shows the confusion matrix for the KNN algorithm used in the decoder and it is another way of looking at its performance. For example, class 2 was sent and class 2 was obtained during all 200 trials but for class 5 the algorithm obtained 3 classes 4, 184 classes 5 and 13 classes 6. In this analysis, from a total of 6,400 signals sent, 102 were incorrect, alternatively it can be said that from a total of 32,000 bits coded, 102 bits were incorrectly decoded which represent a 3.2x10-3-bit error rate (BER). This BER is low for an optical fibre communication system if it were used as a modulation scheme, but it is an interesting result for applications in which the angular position of a device needs to be determined and the information transmitted through an optical fibre . The experiment was done using a specialty fibre single mode at 633 nm, but it can easily be replicated using a standard SMF-28 single mode fibre at 1550 nm, only the optical elements must be chosen for this wavelength. It is important to emphasize that 32 polarizations states have been sent through a non-polarizing optical fibre and estimated correctly 99.02 % of the time.