a days, 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 Microwve Photonic Filter (MPF) and its application. We
investigate all possible set up for MPF and its frequency response and also
analyse spectrum of the laser source used.
Keywords-: Microwave photonic filter(MPF);
single mode standard fibre(SM-SF); Multiwavelength Brillouin-erbium fiber
laser (BEFL); multimode laser diode(MLD).
In present situation, new term radio over
fibre (Rof) technology is discussed. In these technology radio signal is
transmitted using photonic device and optical fibre. For these set up is used
is known as MPF. In addition tunability and reconfigurability of the frequency
response is great attention for researcher. Rof has improvement in terms of
reliability, immune to electromagnetic interference (EMI), tunability over
large bandwidth and low loss. Here analog optical link provide important
advantage 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 independent tunable laser diodes, spectrum slicing of broadband
optical source and the usage of multimode Fabry-Pérot (FP) laser 2.
This paper mainly contains various set up
for MPF which is analysed and from that which type of frequency response would
get and how that set up is used for communication purpose. 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 about two types of laser diode: 1) Multiwavelength Brillouin-erbium fiber laser
(BEFL) and 2) multimode laser diode.
Brillouin-erbium fiber laser (BEFL)
Multiwavelength brillouin-erbium fiber laser MPF is designated and
experimentally described in 2. Figure
1 shows the representation of MPF using BEFL as optical source. BEFL arrangements operate at the linear gain of erbium-doped fiber
amplifier (EDFA) and Brillouin gain in 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 2.FSR is given by
Where D is the total dispersion of
the dispersive medium and ? is the wavelength spacing between adjacent
In figure 1 The BEFL consists 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 analyser using an electro-optic modulator
(EOM) is modulated on 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) 2.
Figure 1. Schematic of MPF with BEFL as a
above set up for MPF, the magnitude of frequency response is given by as 3
Where R=photodetector responsivity, ?0=central
wavelength, N=total number of optical carriers, Pn=optical power
of tap n.
2(b) shows the optical spectrum of the BEFL and Figure 2(c) shows the frequency
response of the MPF in which BEFL is used as optical source and 8 tap 2.
2. (a) Frequency response of MPF where solid line used for experimental and
dashed line used for simulation. (b) Optical spectrum of BEFL before (blue) and after (green) the PSP. The spectral profile of
the PSP is shown in red.
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), polarization controller (PC), mach zehnder intensity
modulator (MZ-IM), single mode standard fibre (SM-SF), photo diode (PD).
Basic topology for MPF 3
As per 4 frequency response of MPF is
directly proportional to the spectrum of laser diode used. So for periodicity
of the response MLD is important. To obtain good optical stability OI is used
because it avoids reflection of MLD. To control 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 optical
carrier signal. After modulator, modulating signal is enter into SM-SF and then
these optical signal converted into electrical signal using PD. Then output
signal is analyse using electrical spectrum generator.
In the frequency response of MPF central
frequency of band-pass window is given as 4 is
And the bandwidth at 3-dB of the
band-pass window is given by 4
Where is optical bandwidth of the MLD. The MLD used
in these experiment 4 is (OKI-OL5200N-5) is as shown in figure 4.
4. Spectrum of MLD 4
Using set up shown in figure 3 we can
transmit wireless signal and TV signal. Here figure 5 shows transmission of
wireless signal of 0.915 GHz 5 and figure 6 shows transmission of TV signal
of 67.25 MHz 4.
Proposed system to transmit a stable reference signal of 0.915 (GHz) through
25.25 (km) of optical fiber 5
Experiment set up to transmit a TV signal of 67.25 MHz through 20.70 (km) of
optical fiber. 4
As per application we can select MLD and
SM-SF. For transmission of wireless signal in 5 they select the MLD is
optically described by an optical spectrum analyzer obtaining: ?0=1533.29 nm,
??=1.1 nm and ??=4.10 nm and SM-SF is of 25.25 km. Using these parameter
frequency response is as shown in figure 7. In these case frequency range is
0.01-10 GHz and central frequency of ban-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, ??=1.00 nm and
??=5.65 nm and SM-Sf is of 20.70 km. Using these parameter frequency response
is as shown in figure 8. In these case frequency range is 0.01-4 GHz and
central frequency of band-pass window is 2.8 GHz. And bandwidth of the window
is 543.70 MHz 4.
Measured frequency response of MPF 5
Measured frequency response of MPF 4
Using BEFL, we analyze the MPF and its
frequency response in which two band-pass window is getting in the frequency
range of 0-5 GHz. Same way using different parameter of MLD and SM-SF we can
get appropriate frequency response. These parameters are FSR of optical source,
dispersive parameter and length of fibre used. As per application we can decide
parameter of MLD and SM-SF. Here two application is described one is
transmission of wireless signal and another is transmission of TV signal.
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