We demonstrate a new scheme for generation of optical frequency comb (OFC) based on cascade modulators, 23 comb lines within 0.5 dB spectral power variation are obtained. An optical finite impulse response (FIR) filter is introduced for suppression of amplified spontaneous emission noise. It is shown that carrier-to-noise-ratio of the OFC generated by this scheme can be as high as 38.8 dB with 12 dB improvement by using a 16-tap FIR filter, and the error vector magnitude performances of loaded Nyquist-16 quadrature amplitude -modulation signal is improved from 14.20% to 7.44%.

We propose a novel in-band optical signal-to-noise ratio (OSNR) monitoring method based on polarization interference. The method realizes a monitoring accuracy of ±0.5 dB within the range of 9–34 dB. Our results indicate that the proposed method is transparent to bitrate and modulation format, as well as independent of polarization mode dispersion and chromatic dispersion.

A two-wavelength sinusoidal phase-modulating (SPM) laser diode (LD) interferometer for nanometer accuracy measurement is proposed. To eliminate the error caused by the intensity modulation, the SPM depth of the interference signal is chosen appropriately by varying the amplitude of the modulation current periodically. Then, the refine theory is induced to the measurement, and the two-wavelength interferometer (TWI) is combined with the single-wavelength LD interferometric technique to realize static displacement measurement with nanometer accuracy. Experimental results indicate that a static displacement measurement accuracy of 5 nm can be achieved over a range of 200 \mu m.

A high channel-count comb filter based on multi-concatenated sampled chirped fiber Bragg gratings (MC-SCFBGs) is proposed and optimally designed by using several chirped gratings with different fundamental grating periods, instead of non-grating sections of SCFBGs. The numerical simulations of the reflection spectra show that the channel spacing and the channel bandwidth in MC-SCFBGs are smaller than those in multi-concatenated chirped fiber Bragg gratings (MC-CFBGs) and that the spectral bandwidth of MC-SCFBGs can be greatly broadened by increasing the cascade number of the grating sections in each sampling period.

Thin film optical coatings tailor light reflected or transmitted from an optical element in a desired way. An optical coating chamber is a complex system in which multiple subsystems operate together to fabricate such coatings. For physical vapor deposition processes, such as evaporation and sputtering, the active parts of the subsystems are located within a vacuum chamber. One example is the source system that provides vapor from which films are formed. A gas delivery subsystem may add process gases either in their ground or excited states. Rotary motion and masking subsystems may be used to achieve better uniformity. In addition, a subsystem that ensures accurate layer thickness control may be utilized. Precision optical coatings require that individual layer thicknesses be controlled to within a few percent of the design target or less to achieve accurate placement of a spectral feature. Systems for manufacturing precision optical coatings demand the use of the subsystems that operate within tight tolerances. In this letter, we illustrate subsystem requirements by examining three examples in detail. We then discuss spectral placement impact resulting from height variations of the substrate mounting, thermal gradients on a substrate, and process instabilities from a moving anode. Finally, we conclude by providing a few examples of the performance attainable using a precision coating platform, when all subsystems work properly.

A robust external cavity diode laser (ECDL) insensitive to mechanical vibration is built with an interference filter for selecting wavelength and a cat-eye reflector for light feedback. The free-running laser has a linewidth of 72 kHz. The laser frequency stability reaches 3×10^-12 at 1-s integration time in terms of relative Allan variance based on the saturation absorption spectrum.

A design approach is described to achieve spectral blocking filters of any spectral width and optical density for narrow blocking bands. We give new criterions to find the necessary number of layers from the desired bandwidth and optical density, and give new estimate equations which describe the number of layers required for designing a blocking filter of given bandwidth, high index, and optical density. This approach can be useful for laser line blocking, night vision filters, and many other general applications.

A photonic heterostructure with multi-channel and sharp angular defect modes by combining two different one-dimensional defective photonic crystals is proposed. The filters designed on the basis of this heterostructure possess both functions of multi-channel narrow band filtering and sharp angular filtering. The channels, channel interval, and number of channels can be tuned by adjusting the geometric and physical parameters of the heterostuctures. This kind of filters will benefit the development of multi-channel interstellar or atmosphere optical communication.