Review work on Microwave Photonics, an upcoming branch

1. Microwave Photonics
– From Concepts to
Applications
ORIGINAL AUTHORS: DIETER JÄGER AND ANDREAS STÖHR
REVIEWER: ROMIL SHAH (10BEC093), INSITITUE OF TECHNOLOGY,
NIRMA UNIVERISTY

2. Abstract
Microwave photonics can be generally defined as the study of high-speed photonic devices
operating at microwave or millimeter wave frequencies and their use in microwave or photonic
systems. In this multidisciplinary field at the interface between microwave techniques, ultra fast
electronics and photonic technologies, typical investigations include, for example, high-speed
and microwave signal generation, processing and conversion as well as the distribution and
transmission of microwave signals via broadband optical links. From pioneering experiments in
the 70´s, this field of microwave photonics has paved the way for an enabling novel technology
with a number of commercially important applications. This paper is intended to give an
overview on this multidisciplinary field of microwave and millimeter wave photonics.

3. 1. Introduction
Term of microwave photonics was introduced in 1991 and used to describe novel optoelectronic
components based upon the interaction of traveling optical and microwaves
Microwave technologies are used and employed in photonics and photonic technologies are
utilized in microwave techniques
Three technologies involved: (i) Ultra fast photonic components such as optical modulators and
detectors with special emphasis on traveling wave devices, (ii) Broadband analog optical links for
high-speed interconnects, (iii) Microwave photonic systems based upon the merging of
microwave and optical technologies

4. 2. Microwave Photonics Components
Electronic devices are usually scaled down with respect to the lateral dimensions
High frequencies the packaging of highspeed devices or circuits has basically to include wave
propagation effects
Interaction between electrons, electrical fields and photons take place which can be regarded as
microwave-optical interactions

5. Microwave optical interaction devices with vertical (a) and horizontal (b) light wave propagation

6. Traveling wave (TW) device where wave
propagation effects in the electrical as well in
the optical domain are utilized
Concept is based on the fundamentals of
nonlinear optics where interaction takes place
during wave propagation

7. Broadband photonic communication networks, the electroabsorption modulator (EAM) will be a
key element because it can be used also as an electroabsorption detector (EAD)
EAM lumped element exhibits a RC time constant corresponding to about 10 GHz whereas the
TW EADdevice shows a clear response beyond 160 GHz
Use of microwave technologies can drastically improve the bandwidth of such photonic devices

8. A comparison is made between a lumped EAM and a TW EAD with comparable cross sections.

9. 3. Broadband Fiber Optical Links
Transmitting side a cw laser diode and an external modulator (electrooptic or EAM) and on the
receiving side an optoelectronic photodetector can be used
Link gain can easily be achieved when an optical amplifier (EDFA) and/or external modulators,
preferably on both sides, are being used

10. The great advantage is that due to the
broadband low-loss transmission
capability the optical fiber can ideally be
used to transmit microwave signals and
therefore replace other lossy metallic
waveguides, e. g. X-band WG or coax
Propagation loss of different transmission
media, SM = single mode and MM =
multimode glass fiber

11. 4. Microwave Photonic Systems
Broadband fiber optic links are regarded to be basic building blocks for different microwave
systems:
(i) Photonic signal generation and local oscillators
(ii) EMC sensor
(iii) Optoelectronic testing
(iv) Hybrid fiber-coax systems
(v) Fiber-radio systems
(vi) Antenna systems

12. (i) Photonic signal generation and local
oscillators
Concept of UWB signal generation using a
microstrip resonator with an optoelectronic switch
as an RF mirror integrated with a broadband
antenna
Difference frequency is photonically generated by
heterodyne techniques and where wavelength
tuning provides a bandwidth of several THz
depending on the bandwidth of the detector

13. (ii) EMC sensor
Modulator at the end of a fiber is driven by an electrical input signal
Received optical signal can be used to measure the electrical signal quantitatively at Tx side
Electrical dc power required at the sensor side can also be transmitted optically by employing a
photovoltaic cell at Rx side

14. (iii) Optoelectronic testing
Microminiaturized modulator chip working in
reflection mode and coupled to the end of a fiber
Basic concept for contactless high-speed testing of
integrated circuits, well-known as the electrooptic
sampling principle

15. (iv)Hybrid fiber-coax systems
In cable TV (CATV) the signals received from TV satellites can be converted into the optical
domain
Also fed into a fiber to be transmitted over long distances with only small attenuation
Optical signals being transmitted are converted back into the electrical domain and guided to
the costumer via coaxial cable

16. (v) Fiber-radio systems
Broadband services the frequencies are in the millimeter wave range
Concept is based upon an optical link between the central station (CS) and the base station (BS)
in a pico cellular structure
A novel architecture of a 60 GHz fiber-radio system using an EAT
(i) to generate the 57 GHz carrier frequency from LD1 and LD1’ where LD1 is directly
modulated by the downlink IF signal at 2.6 GHz
(ii) to mix the photonic LO signal directly with the IF signal

17. Architecture for a 60 GHz fiber-radio access system [23]. LD denotes a laser diode, PD a
photodetector, and EAT-X an EAT – mixer. MT is the mobile terminal

18. (vi)Antenna systems
A major application of optical link technology is the remoting of antenna systems and,
particularly, the optical control of array antennas
A millimeter wave or THz camera with photonic interconnection is foreseen

19. Thank You