An overview of analog microwave photonics will be presented. The performance requirements for externally-modulated analog microwave photonic links will be reviewed with specific emphasis placed on modulator efficiency, laser noise, detected photocurrent, and link linearity.

http://ieeexplore.ieee.org/iel5/6387506/6403300/06403360.pdf

Microwave photonics

An applications-oriented review of optical parametric amplifiers in fiber communications is presented. The emphasis is on parametric amplifiers in general and single pumped parametric amplifiers in particular. While a theoretical framework based on highly efficient four-photon mixing is provided, the focus is on the intriguing applications enabled by the parametric gain, such as all-optical signal sampling, time-demultiplexing, pulse generation, and wavelength conversion. As these amplifiers offer high gain and low noise at arbitrary wavelengths with proper fiber design and pump wavelength allocation, they are also candidate enablers to increase overall wavelength-division-multiplexing system capacities similar to the more well-known Raman amplifiers. Similarities and distinctions between Raman and parametric amplifiers are also addressed. Since the first fiber-based parametric amplifier experiments providing net continuous-wave gain in the for the optical fiber communication applications interesting 1.5-/spl mu/m region were only conducted about two years ago, there is reason to believe that substantial progress may be made in the future, perhaps involving "holey fibers" to further enhance the nonlinearity and thus the gain. This together with the emergence of practical and inexpensive high-power pump lasers may in many cases prove fiber-based parametric amplifiers to be a desired implementation in optical communication systems.

/pdf/fiber-based-optical-parametric-amplifiers-and-their-191pg0fmcj.pdf

Fiber-based optical parametric amplifiers and their applications

The low-loss wide bandwidth capability of opto-electronic systems makes them attractive for the transmission and processing of microwave signals, while the development of high-capacity optical communication systems has required the use of microwave techniques in optical transmitters and receivers. These two strands have led to the development of the research area of microwave photonics. This paper reviews the development status of microwave photonic devices, describes their systems applications, and suggests some likely areas for future development

Microwave Photonics

We review photonic applications of dielectric whispering-gallery mode (WGM) resonators-tracing the growth of the technology from experiments with levitating droplets of aerosols to ultrahigh-Q solid state crystalline and integrated on-chip microresonators.

Optical resonators with whispering-gallery modes-part II: applications

Whispering-gallery modes (WGM) on a spherical surface were first described by Lord Rayleigh at the beginning of the last century, but only after the invention of laser did they start to have some scientific relevance and only during the last two decades there has been a substantial move towards real devices and practical applications. WGM resonators have peculiar properties, the most notable being the potential of having an ultrahigh quality factor Q, which makes them very appealing both as laser cavities and as extremely sensitive sensors. Among the different types of WGM resonators, the microspherical ones represent a very important category, due to their simplicity, easy fabrication, and very high quality. In this review we provide a description of their fundamental properties and we summarize recent works on their application as filters, sensors and lasers.

Spherical whispering‐gallery‐mode microresonators

An all-optical passive four-port system including a fused silica microsphere and two tapered fibers is proposed and demonstrated for the application as a channel adding-dropping device. It is shown that channels can be selectively exchanged between two fibers by coupling to a whispering gallery mode resonance in the microsphere. Finesse in excess of 11150 is measured for the loaded whispering gallery modes.

/pdf/fiber-optic-add-drop-device-based-on-a-silica-microsphere-jlrh4slmrz.pdf

Fiber-optic add-drop device based on a silica microsphere-whispering gallery mode system

A resonant optical modulator comprises a transmission fiber-optic waveguide, a circumferential-mode optical resonator transverse-coupled thereto, a modulator optical component transverse-coupled to the circumferential-mode resonator, and a modulator control component. A control signal applied to the modulator optical component through the modulator control component alters the round-trip optical loss of the circumferential-mode resonator, thereby altering the transmission of a resonant optical signal through the transmission fiber-optic waveguide. The modulator optical element may comprise an open waveguide or a closed waveguide (i.e., resonator). The resonator round-trip optical loss may be altered by altering the optical absorption/scattering of the modulator optical component, by altering the amount of optical power transfer between the resonator and the modulator optical component, or by altering an optical resonance frequency of a resonant modulator optical component.

Resonant optical modulators

An optically based resonating sensor useful for detecting and discriminating specified substances present in the environment is provided. The resonating sensor comprises a light source and a coupler adapted to allow light to pass from the light source to a resonator wherein the light is stored for a specified period of time. The resonator is coupled to the coupler such that some portion of the light passing through the coupler enters the resonator and some portion of the light resonating within the resonator exits the resonator to the coupler. The outer surface of the resonator is modified such that the interaction of the modified outer surface of the resonator with a specified substance in the environment alters some characteristic of the light flowing through the sensor system. A detector is arranged to observe and detect the interactions between the modified outer surface and the light flowing through the system.

Optical resonator microsphere sensor with altering Q-factor

A resonator (300), e.g., a silica microsphere or disk, is used between two fiber optic cables (500, 502) to form an add/drop filter. The resonator (300) is resonant with the frequency to be added or dropped. In this way, only that particular channel is added or dropped as needed.

Resonator fiber bidirectional coupler

A resonant optical filter including a first and second transmission optical waveguides (600, 602) and a resonator, which resonator may include one or more resonator segments evanescently optically coupled therebetween. The resonator supports a circumferential resonant optical mode and is evanescently coupled to each of the first and second transmission optical waveguides. In a preferred embodiment, an optical signal entering the resonant optical filter through the first transmission optical waveguides (600) and substantially resonant with an optical resonance of resonator is substantially transferred to the second transmission waveguide (602), while an optical signal entering the resonant optical filter through the first transmission optical waveguide (600) and substantially non-resonant with an optical resonance of the coupled-optical resonator system substantially remains in the first transmission optical (600) waveguide and leaves the resonant optical filter through the first transmission optical waveguide (600).

G. Hunziker

Papers

Fiber-optic add-drop device based on a silica microsphere-whispering gallery mode system

Resonant optical modulators

Optical resonator microsphere sensor with altering Q-factor

Resonator fiber bidirectional coupler

Resonant optical filters