Abstract: Wavelength multiplex transmission is realized in which the temperature dependency of an EDFA is compensated for in relation to the wavelengths which are used. A first and a second long-period grating which have different periods from each other are formed in an optical fiber, ensuring that the peak wavelength of a waveform representing an optical transmission loss characteristic of the first long-period grating side is located on the shorter wavelength side than a transmission band and a peak wavelength of a waveform representing an optical transmission loss characteristic of the second long-period grating side is located on the longer wavelength side within the transmission band.

Abstract: An etalon filter of the invention is an etalon filter where the light transmission property depending on temperature is reduced, which is preferable as an optical device. An etalon filter (11) has a filter main body (1) where reflecting films are disposed on a light input side surface and a light output side surface of a light transmission medium. The etalon filter (11) is formed by disposing different linear expansion coefficient members (2) having a coefficient of linear expansion different from that of the light transmission medium in areas on both sides of the filter main body (1) except optical path length areas (4).

Abstract: The present invention effectively compensates gain wavelength dependency of optical amplifiers by a simple method. That is, a value smaller than the minimum value of gain, in the range of usage wavelengths, of gain wavelength dependency data of the optical amplifiers is predetermined as a reference gain value. A loss wavelength characteristic which counterbalances the gain greater than the reference gain value is provided as an ideal loss wavelength characteristic which completely compensates the gain wavelength dependency.

Abstract: In an optical gain equalizer according to the present invention, a plurality of etalon filters 1 and one ore more fiber gratings 2 or dielectric multilayer filters 3 are arranged in line, and a beam of light externally applied is passed through the etalon filters 1 and the fiber gratings 2 or dielectric multilayer filters 3 and outputted to the outside, and the etalon filters 1 have sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening, and the one or more fiber gratings 2 or dielectric multilayer filters 3 compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters 1. An optical amplifying device 14 is constituted by combining an optical amplifier 5 with the optical gain equalizer 4.

Abstract: An optical filter apparatus and a method of designing an optical filter having a target loss wavelength characteristic. The optical filter is formed by combining a plurality of optical parts, each having a periodic loss wavelength characteristic with respect to the wavelength. The loss wavelength characteristic may be determined using a theoretical equation that includes phase and amplitude determining parameters. Nonlinear fitting is used to determine first optimum solutions for respective phase determining parameters from predetermined numerical values. Additionally, groups of numerical values are determined from numerical ranges in the vicinities of the first optimum solutions and nonlinear fitting analysis. Consequently, optimum solutions are successively calculated and respective parameters are determined to reach final optimum solutions. Finally, the determined parameters are used to approximate the loss wavelength characteristic of the optical filter.

Abstract: An optical filter having a precise optical thickness is produced by controlling the optical thickness of the film formed on the product substrate precisely. The optical thickness of the film formed on the monitoring chip 2 and the data of the relation of this optical thickness to the reflectance of the film are determined beforehand and used as film thickness control data. On arranging both the product substrate 3 and the monitoring chip 2 within the film forming area 7 to form films on these substrates simultaneously, the correction coefficient for correcting the amount of deviation of the optical thickness of the film formed on the product substrate 3 from the optical thickness of the film formed on the monitoring chip 2 is provided by the film thickness correction coefficient data determined beforehand, for example for each film material and according to the monitor light wavelength.

Abstract: Wavelength multiplex transmission is realized in which the temperature dependency of an EDFA is compensated for in relation to the wavelengths which are used. A first and a second long-period grating which have different periods from each other are formed in an optical fiber, ensuring that the peak wavelength of a waveform representing an optical transmission loss characteristic of the first long-period grating side is located on the shorter wavelength side than a transmission band and a peak wavelength of a waveform representing an optical transmission loss characteristic of the second long-period grating side is located on the longer wavelength side within the transmission band.

Abstract: The temperature dependency of an EDFA is compensated in a wavelength of 1570 to 1600 nm to realize a wavelength division multiplexing transmission. First and second long period gratings different in grating period from each other are formed in an optical fiber. The peak wavelength of the waveform of the light transmission loss characteristic of the first long period grating is formed on the shorter wavelength side than a transmission band. The peak wavelength of the waveform of the light transmission loss characteristic of the second long period grating is formed on the longer wavelength side than a transmission band.

Abstract: An ink composition contains a carrier medium and charged particles containing a coloring agent, which ink composition satisfies at least one condition of condition A or B: condition A that the specific charge quantity of the charged particles is in a range of 10 to 1,000 .mu.C/g with a positive or negative polarity; and condition B that the specific resistance of the ink composition is 10.sup.10 .OMEGA.cm or more; and ink-jet recording methods using the ink composition are proposed.

Abstract: A developer for use in electrophotography for developing latent electrostatic images to visible toner images, includes at least two kinds of toner particles with different shapes selected from the group consisting of spherical toner particles, fibrous toner particles and amorphous toner particles, each toner particle containing a coloring agent and a binder resin. There is provided a liquid developer including a toner which is dispersed in a carrier liquid, in which the toner includes at least two kinds of the above-mentioned toner particles with different shapes. An electrophotographic image formation method using the above-mentioned liquid developer is also provided.