Kazuya MIYAGI^*, Yoshinori NAMIHIRA, S. M. Abdur RAZZAK¹, Shubi F. KAIJAGE¹, and Feroza BEGUM¹

Electrical and Electronics Engineering, Faculty of Engineering, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan
¹Graduate School of Engineering and Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan

(Received January 25, 2010; Accepted February 22, 2010)

We have demonstrated that the correction factor k_n = A_eff/(π w²), where w = MFD/2 (MFD: mode field diameter), is above 1.20 for photonic crystal fibers (PCFs) with structural parameters in the range of d/Λ ≅ 0.40 to 0.90 (d/Λ: ratio of hole diameter d and pitch Λ). By using the far-field scanning (FFS) technique and the finite difference method, the results of experimental measurements and numerical simulations differed by only 0.9 to 3.0% for two types of PCFs. The finding that k_n ≠ 1.0 for PCFs indicates that their electrical field distribution is non-Gaussian and cannot be determined by assuming a conventional step-index distribution for PCFs. It was also found that the ITU-T Petermann II definition is the most suitable for MFD measurements of PCFs with non-Gaussian distribution.

Key words: photonic crystal fiber (PCF), pure silica core fiber (PSCF), mode field diameter (MFD), effective area (A_eff), correction factor (k_n)

^*E-mail address: miyagi@eee.u-ryukyu.ac.jp