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To compensate for the temperature dependency of a standard FBG, a cladding-etched FBG immersed with a liquid mixture having a negative thermo-optic coefficient is presented, and its characteristics are investigated. The Bragg wavelength of the cladding-etched FBG is shifted counter to the direction of the Bragg wavelength shift of a conventional FBG according to the mixing ratio of glycerin to water; thus, the temperature-dependent Bragg wavelength shift was almost compensated by using a liquid mixture of water (50%) and glycerin (50%) having the negative thermo-optic coefficient of −5 × 10−4 °C−1.

Two types of 4 4 plastic optical fiber star couplers incorporated with a polymer waveguide as the optical power distributor are proposed, and their high performances are demonstrated. The characteristics of the proposed star coupler are investigated based on ray optics, and its power distribution performance is evaluated in terms of the flatness of the coupling ratio and the amount of the excess loss. Under the best conditions, the flatness of the coupling ratio and the excess loss of the fabricated device have been obtained as 2.0 dB and 2.5 dB, respectively.

The temperature sensitivity of fiber Bragg grating (FBG) temperature sensor is enhanced when using a copper tube to jacket of the FBG.Both sides of the FBG are glued with epoxy to cylindrical ferrules tubes that in turn is inserted and glued to a cylindrical copper tube. As the high thermal expansion coefficient of the cylindrical copper tube pulls both sides of the FBG, the temperature sensitivity is improved 3.3‐fold when compared to that of a bare FBG. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26032

Over the past five years two teams have used type Ia supernovae to trace the expansion of the universe to a look-back time more than 70% of the age of the universe. These observations show an accelerating universe which is best explained by a cosmological constant, or other form of dark energy with an equation of state near w = p/ρ = −1. There are many possible lurking systematic effects. However, while difficult to completely eliminate, none of these appears large enough to challenge current results. However, as future experiments attempt to better characterize the equation of state of the matter leading to the observed acceleration, these systematic effects will ultimately limit progress.PACS numbers: 9575D, 9575W, 9585K, 9760B, 9880E