An analytic model is developed to study the dynamic response of carrier-depletion silicon ring modulators. Its validity is confirmed by a detailed comparison between the modeled and the measured small signal frequency response of a practical device. The model is used to investigate how to maximize the optical modulation amplitude (OMA) and how the OMA could be traded for the bandwidth by tuning the coupling strength and the operation wavelength. Our calculation shows that for a ring modulator with equal RC time constant and photon lifetime, if its operation wavelength shifts from the position of the maximum OMA towards the direction that is away from the resonance, the 3dB modulation bandwidth increases ~2.1 times with a penalty of 3 dB to the OMA.

We investigated experimentally and theoretically an invertible fiber-type transformation from a photonic bandgap fiber into a nonideal waveguide and then into an index-guiding photonic crystal fiber via the thermo-optic effect of the fluid filled in the air holes. Such a transformation could be used to develop an in-fiber optical switch/attenuator with a high-extinction ratio of more than 35 dB over an extremely broad wavelength range from 600 to 1700 nm via a small temperature adjustment. -6]. The fiber type transformation from a PCF into a PBF should be an invertible process resulting from increasing/decreasing the refractive index of the filled materials. Such an invertible transformation in the fiber types (PCF/PBF) may lead to many potential applications. Research [1][2][3][4][5][6] was, however, focused on the transformation from an index-guiding fiber to a bandgap-guiding fiber instead of an opposite process. In this Letter, we filled a fluid into the air holes of a solid-core PCF and investigated experimentally and theoretically an invertible fiber-type transformation from a PBF into an unideal waveguide and then into an index-guiding PCF via the thermo-optic effect of the filled fluid. Such a fluid-filled PCF could be used to develop an in-fiber optical switch/attenuator with a high extinction ratio of more than 35 dB over an extremely broad wavelength range from 600 to 1700 nm.We employed a large-mode area PCF (LMA-10 from Crystal Fibre) with a core diameter of about 5.9 m in which the air holes with a diameter of 3.2 m are arranged in a hexagonal pattern with a pitch of 7.5 m, as shown in Fig. 1(a). One end of the PCF with a length of 500 mm was spliced to a standard single-mode fiber (SMF) with a splice loss of about 1.5 dB using the arc fusion-splicing technique [7]. Another end of the PCF was cleaved and then immersed into a refractive-index-matching liquid with a thermo-optic coefficient of −4.15ϫ 10 −4 /°C from Cargille Labs (n = 1.550 at room temperature, http:// www.cargille.com). The fluid was filled into air holes in the PCF with the well-known capillary action, as shown in Figs. 1(b)-1(d). The fully filled PCF has a total length of about 200 mm.Then the opening end of the fluid-filled PCF was butt-coupled to another conventional SMF in order to investigate its transmission spectrum with a supercontinuum white-light source (KOHERAS SuperK Compact) and an optical spectrum analyzer (ANDO AQ6317B). The fluid-filled PCF was placed in a column oven (LCO 102) to investigate its transmission spectra at different temperatures. Figure 2(a) illustrates the measured transmission spectra of the fluid-filled PCF at temperatures of 20°C, 60°C, and 100°C, where the total insertion loss of about 5 dB is attributed to the coupling losses between the PCF and the two SMFs. As shown in the transmission spectrum at 20°C, three clear attenuation gaps were observed within the wavelength range from 750 to 820 nm, from 950 to 1050 nm, and from 1300 to 1550

This paper describes woven fabrics made from polymer optical fibers (POF), which are treated with a CO 2 laser so that the resultant surface notches on the POFs facilitate side emission of light. The transmission and side-emitting behavior of POF with surface notches are studied in term of the variation in bending curvatures, which is related to end-usage of the woven fabrics as flexible displays, wearable phototherapy devices and fashion accessories. The measured power of transmission of light from the POF rapidly decreases with increasing bending curvature. However, the measured power of side-emission of light from the notched POFs remains almost constant at various bending curvatures within the experimental range. Theoretical analysis of the light propagation in a notched POF is conducted, which illustrates that more light is reflected from one side of the notch when the bending curvature is increased hence the transmission of the light is decreased. The theoretical and experimental results reach a good agreement.

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