We present a novel scheme for simultaneous measurement of the external RI and temperature by using the sandwiched long-period gratings (SLPGs). An LPG pair coupling between the guided mode and the low-order cladding mode acts a temperature reference element, and another LPG in-between coupling with the higher-order cladding mode performances an RI sensor. The period and length of the paired LPG (with a center to center distance 47.5mm) are 643 μm and 22.5mm, respectively, and those of LPG in-between are chosen to be 428 μm and 23mm, respectively. The experimental results show that the RI sensitivities of a paired LPG coupling with the third order cladding mode is -6.71 nm/R.I.U (refractive index unit), and the sensitivity of the LPG in between coupling with the ninth order cladding mode is
-27.77 nm/R.I.U. The temperature sensitivities of these LPGs are
-0.315nm/°C; and -0.337nm/°C;, respectively.
We present the design and fabrication of a broadband all-fiber wavelength-division multiplexing (WDM) filter based on the long-period grating (LPG) technology. By utilizing the improved LPGs, i.e. the LPG with step-changed index modulation, an LPG with a 3-dB flat-bottom stop-band was designed with transfer matrix method. The fabrications of the designed LPG and the broadband WDM filter are also realized by using the point-by-point grating writing technique in the experiments.
The benefits of using multi-granularity switching to reduce the number of ports, including both electronic and optical ports, have been investigated. A multi-layer ring architecture with multiple switches is suggested and two equations to count the number of ports are derived. Comparisons are made among multi-layer multi-granularity switching (MM-XC), multi-switching (M-XC), and single switching (S-XC).