Various Scheme of Set Up for Microwave Photonic Filter and Its Application

Nowadays, the interface between microwave engineering and photonic technology is used in the field of communication and these new interdisciplinary is known as Microwave Photonics (MWP). This paper describes various set up for Microwave Photonic Filter (MPF) and its application. We investigate all possible set up for MPF and its frequency response and also analyze the spectrum of the laser source used.

In the present situation, new term radio over fiber (RoF) technology is discussed. In this technology, the radio signal is transmitted using the photonic device and optical fiber. For these set up is used is known as MPF. In addition tunability and reconfigurability of the frequency response is great attention for the researcher. Rof has improvement in terms of reliability, immune to electromagnetic interference (EMI), tunability over a large bandwidth and low loss. The here analog optical link provides important advantages such as receiver sensitivity and possible usage of analog modulation. Potential applications of analog optical links include antenna remoting, cable television systems, phased array radar and interconnection of microwave systems [1]. Different processes of multi-source MPFs have been predicted, including the use of independently tunable laser diodes, spectrum slicing of the broadband optical source and the usage of multimode Fabry-Prot (FP) laser.

This paper mainly contains various set up for MPF which is analyzed and from that which type of frequency response would get and how that set up is used for communication purpose. The survey has been done on methods of providing internet onboard but it has not included new technologies.

For MPF we can use various type of optical source. In this paper we discuss two types of laser diode: 1)Multiwavelength Brillouin-erbium fiber laser (BEFL) and 2) multimode laser diode.

Using Multiwavelength Brillouin-erbium fiber laser MPF is designated and experimentally described in [2]. Figure 1 shows the representation of MPF using BEFL as the optical source. BEFL arrangements operate at the linear gain of erbium-doped fiber amplifier (EDFA) and Brillouin gain in the optical fiber to understand multiwavelength lasing. By adjusting the pump power, the number of lasing channels in BEFL can be easily controlled that is used to pump the erbium-doped fiber for precise controlling of optical taps. Since the wavelength spacing of 0.089 nm between adjacent channels is very small in this case, adequate adjustment of the filter discernment can thus be achieved. In figure 1 The BEFL consists of standard single mode fiber (SMF) of a length of 5 km and EDF of a length of 10 m, confined in between two Faraday mirrors. To deliver pump power to the EDF, a 980 nm laser diode was used. A tunable laser source as the Brillion pump (BP) was coupled to the cavity via a 3-dB coupler [2]. Tuning the EDF pump power adjusts the number of output wavelengths accordingly, whereas varying the BP wavelength changes the output wavelengths of the laser. To modify the spectral profile of BEFL, the programmable spectral processor (PSP) is used [2]. The radio frequency (RF) signal from a network analyzer using an electro-optic modulator (EOM) is modulated on the carrier signal. The regular gain region of an EDFA was utilized to ensure linear amplification of the modulated signal before it was sent through a dispersive medium, which was a 23 km dispersion compensation fiber (DCF) [2]. The DCF has a chromatic dispersion of about -245 ps/nm/km, which gives a total accumulated dispersion of -5635 ps/nm [2]. An optical-to-electrical conversion was performed with a 70 GHz photodetector (PD) (XPDV3120R from u2t).

Using Multimode laser diode.

The main topology for MPF used in [4] is as shown in figure 3. It is mainly established multimode laser diode (MLD), optical isolator (OI), a polarization controller (PC), each Zehnder intensity modulator (MZ-IM), single mode standard fiber (SM-SF), a photodiode (PD).

As per [4] frequency response of MPF is directly proportional to the spectrum of the laser diode used. So for the periodicity of the response, MLD is important. To obtain good optical stability OI is used because it avoids reflection of MLD. To control the output power of MZ-IM polarization controller is required. To give input electrical signal electrical signal generator is used and this electrical signal is modulated on the optical carrier signal. After modulator, modulating signal is enter into SM-SF and then these optical signal converted into an electrical signal using PD. Then output signal is analyzed using electrical spectrum generator.

Using set up shown in figure 3 we can transmit wireless signal and TV signal. Here figure 5 shows transmission of a wireless signal of 0.915 GHz [5] and figure 6 shows transmission of TV signal of 67.25 MHz.

As per application, we can select MLD and SM-SF. For transmission of a wireless signal in [5], they select the MLD is optically described by an optical spectrum analyzer obtaining: 0=1533.29 nm, d=1.1 nm and ?=4.10 nm and SM-SF is of 25.25 km. Using this parameter frequency response is as shown in figure 7. In these case frequency range is 0.01-10 GHz and the central frequency of band-pass window is 2.31, 4.62, 6.86, and 9.14 respectively. And bandwidth of the window is 647.9 MHz [5]. As shown in figure 8 for transmission TV signal in [4] they select the MLD is optically described by an optical spectrum analyzer obtaining: 0=1553.53 nm, d=1.00 nm and ?=5.65 nm and SM-Sf is of 20.70 km. Using this parameter frequency response is as shown in figure 8. In these case frequency range is 0.01-4 GHz and the central frequency of band-pass window is 2.8 GHz. And bandwidth of the window is 543.70 MHz.

Using BEFL, we analyze the MPF and its frequency response in which two band-pass windows is getting in the frequency range of 0-5 GHz. Same way using a different parameter of MLD and SM-SF we can get appropriate frequency response. These parameters are FSR of the optical source, dispersive parameter and length of fiber used. As per application, we can decide parameter of MLD and SM-SF. Here two application is described one is the transmission of the wireless signal and another is the transmission of TV signal.