Optical transmission of microwave (MW) and millimeter-wave (MMW) signals have become an intensive research area in the last decade. There is a growing interest in optical processing of MW signals, phased array applications and wireless distribution of broadband data in fiber-fed MMW subscriber access systems. This paper extends the existing models of MW/MMW optical link that are based on optical intensity (see Frigyes, I. et al., Proc. of the 27th EuMC, 1997; Cox III, C.H. et al., MTT, vol.38, no.5, p.501-9, 1990). The model is suitable for estimating harmonic levels of the MW modulation signal generated in the optical path. Considering a MW fiber-optic link, both the optical transmitter and the receiver are responsible for harmonic generation. Furthermore the optical fiber itself inserted between the transmitter and receiver induces harmonics due to dispersion. Exact modelling of harmonic generation requires a calculation based on the optical field instead of purely on a intensity basis (see Hilt, A. et al., 1999; Maury, G. et al., 1999).

/pdf/microwave-harmonic-generation-in-fiber-optical-links-266wxtulbh.pdf

Microwave harmonic generation in fiber-optical links

This paper is intended to elaborate on the investigation and suppression of the relative intensity noise of a diode pumped Nd:YVO/sub 4/ microchip laser. In addition to noise suppression at the relaxation oscillations, noise analysis is also reported. For these investigations a very simple, rate-equation-based model of the laser transfer function was used.

Noise suppression of Nd:YVO/sub 4/ solid-state lasers for telecommunication applications

The semiconductor optical amplifier (SOA) can be used as an efficient high-speed modulator. This paper presents optical subcarrier multiplexed label swapping/reinsertion utilizing this device associated to the wavelength converter block in packet-switched all-optical networks. For that purpose, the modulation response and nonlinear behavior of SOAs are analyzed and experimentally demonstrated.

Optical subcarrier label swapping by semiconductor optical amplifiers

This paper demonstrates that in broadband networks in-line semiconductor optical amplifiers (SOAs) beside providing system gain can also be used as simultaneous transceivers. The SOA branching stages are studied and presented for bus configuration. Using a steady-state model, we have made a small-signal approximation applying an equivalent circuit for detection based on the rate equations. The theory enables us to explain the detection functionality, the optimal working state of the multifunctional SOA, and to analyze noise properties. The measurements support the calculations. So the SOA-transceivers are potentially useful in subcarrier multiplexed access systems.

Semiconductor Optical Amplifier for Detection Function in Radio Over Fiber Systems

Semiconductor optical amplifiers (SOAs) can be advantageously utilized as external modulators because they can simultaneously perform two functions: amplification and modulation. When the SOA is used in a subcarrier multiplexed system, the modulation linearity is a crucial property. In this paper, theoretical and experimental investigations are presented with the result of improved modulation linearity. By proper adjustment of the operation point and by careful optical matching, a significant improvement in the modulation linearity and also in the spurious-free dynamic range is achieved, along with high modulation sensitivity and wide bandwidth.

Improvements in the Linearity of Semiconductor Optical Amplifiers as External Modulators

An experimental and theoretical study is presented for the transmission characteristics of all semiconductor fiber optic links carrying microwave channels. The nonlinear distortion and signal to noise ratio are investigated and evaluated in case of multi-carrier transmission. Extremely high spurious free dynamic range is presented achieved by a direct modulated semiconductor laser.

Transmission Characteristics of All Semiconductor Fiber Optic Links Carrying Microwave Channels

A new approach for the generation of millimeter wave (MMW) carriers in fiber-radio systems is presented. A subharmonic of the carrier is transmitted to the radio nodes over the fiber-optic network. At each base station the MMW carriers are generated by a phase locked oscillator (PLO) using harmonic mixing technique. Due to the subharmonic reference transmission, chromatic dispersion in the optical path is avoided. Further advantage is the inherent possibility of channel selection to avoid radio interference between adjacent transmitters.

http://ieeexplore.ieee.org/iel4/5628/15097/00700665.pdf

New carrier generation approach for fiber-radio systems to overcome chromatic dispersion problems

The measurement of the nonlinearity parameters is usually cumbersome and not accurate enough In this paper a new method is presented for the measurement of the nonlinearity characteristics, ie for the AM compression and AM-to-PM conversion The new method offers an easy measurement process which is widely applicable It does not need special instrumentation The new method has another important advantage: the dynamic behavior of the nonlinearity characteristics can also be obtained in a simple way Utilizing the new measurement method the nonlinear characteristics of a microwave amplifier have been determined

A new microwave amplifier nonlinearity measurement method

New methods for optical millimeter wave generation are presented. They apply a harmonic oscillator stabilized to an optically transmitted subharmonic reference signal by a frequency division PLL. A 94 GHz signal was generated using both injection and phase locking techniques. The new approaches utilize inexpensive photonic components and exhibit low sensitivity to the fiber dispersion.

https://ieeexplore.ieee.org/iel5/6946/18681/00862317.pdf

Optical millimeter wave generation utilizing a subharmonic reference

This paper is concerned with the suppression of the relative intensity noise (RIN) peak and phase noise of a diode pumped Neodymium-doped Lithium Niobate (Nd:LiNbO/sub 3/) microchip laser. Relaxation oscillations result in about 15-20 dB noise peak above the flat noise at 350 kHz offset frequency. In case of high quality requirements this noise peak is significantly disturbing. In this paper a new approach is presented for the suppression of the RIN peak and phase noise in microchip lasers.

T. Marozsak

Papers

Transmission Characteristics of All Semiconductor Fiber Optic Links Carrying Microwave Channels

New carrier generation approach for fiber-radio systems to overcome chromatic dispersion problems

A new microwave amplifier nonlinearity measurement method

Optical millimeter wave generation utilizing a subharmonic reference

A new approach for RIN peak and phase noise suppression in microchip lasers