Chotaliya Ankitaben G.EC departmentL.D. College of EngineeringAhmedabad, [email protected] Usha NeelkantanHead of EC DepartmentL.
D. College of EngineeringAhmedabad, [email protected]
com Abstract—Nowa days, the interface between microwave engineering and photonic technology isused in the field of communication and these new interdisciplinary is known asMicrowave Photonics (MWP). This paper describesvarious set up for Microwve Photonic Filter (MPF) and its application. Weinvestigate all possible set up for MPF and its frequency response and alsoanalyse spectrum of the laser source used.Keywords-: Microwave photonic filter(MPF);single mode standard fibre(SM-SF); Multiwavelength Brillouin-erbium fiberlaser (BEFL); multimode laser diode(MLD). I. IntroductionIn present situation, new term radio overfibre (Rof) technology is discussed.
In these technology radio signal istransmitted using photonic device and optical fibre. For these set up is usedis known as MPF. In addition tunability and reconfigurability of the frequencyresponse is great attention for researcher. Rof has improvement in terms ofreliability, immune to electromagnetic interference (EMI), tunability overlarge bandwidth and low loss.
Here analog optical link provide importantadvantage such as receiver sensitivity and possible usage of analog modulation.Potential applications of analog optical links include antenna remoting, cabletelevision systems, phased array radar and interconnection of microwave systems1. Different processes of multi-source MPFs have been predicted, includingthe use of independent tunable laser diodes, spectrum slicing of broadbandoptical source and the usage of multimode Fabry-Pérot (FP) laser 2.This paper mainly contains various set upfor MPF which is analysed and from that which type of frequency response wouldget and how that set up is used for communication purpose. Survey has been done on methods of providinginternet onboard but it has not included new technologies.
For MPF we can use various type ofoptical source. In this paper we discuss about two types of laser diode: 1) Multiwavelength Brillouin-erbium fiber laser(BEFL) and 2) multimode laser diode. II. Using MultiwavelengthBrillouin-erbium fiber laser (BEFL)UsingMultiwavelength brillouin-erbium fiber laser MPF is designated andexperimentally described in 2. Figure1 shows the representation of MPF using BEFL as optical source.
BEFL arrangements operate at the linear gain of erbium-doped fiberamplifier (EDFA) and Brillouin gain in optical fiber to understandmultiwavelength lasing. By adjusting the pump power, the number of lasingchannels in BEFL can be easily controlled that is used to pump the erbium dopedfiber for precise controlling of optical taps. Since the wavelength spacing of0.089 nm between adjacent channels is very small in this case, adequateadjustment of the filter discernment can thus be achieved 2.FSR is given by6 (1)Where D is the total dispersion ofthe dispersive medium and ? is the wavelength spacing between adjacentwavelengths.In figure 1 The BEFL consists standardsingle mode fiber (SMF) of a length of 5km and EDF of a length of 10 m, confinedin between two Faraday mirrors. To deliver pump power to the EDF, a 980 nmlaser diode was used.
A tunable laser source as the Brillion pump (BP) wascoupled to the cavity via a 3-dB coupler 2. Tuning the EDF pump power adjuststhe number of output wavelengths accordingly, whereas varying the BP wavelengthchanges the output wavelengths of the laser. To modify the spectral profile ofBEFL, the programmable spectral processor (PSP) is used 2. The radiofrequency (RF) signal from a network analyser using an electro-optic modulator(EOM) is modulated on carrier signal.
The regular gain region of an EDFA wasutilized to ensure linear amplification of the modulated signal before it wassent through a dispersive medium, which was a 23 km dispersion compensationfiber (DCF) 2. The DCF has a chromatic dispersion of about ?245ps/nm/km, which gives a total accumulated dispersion of ?5635ps/nm 2. An optical-to-electrical conversion was performed with a 70 GHzphotodetector (PD) (XPDV3120R from u2t) 2. Figure 1. Schematic of MPF with BEFL as asource 2Usingabove set up for MPF, the magnitude of frequency response is given by as 3 (2)Where R=photodetector responsivity, ?0=centralwavelength, N=total number of optical carriers, Pn=optical powerof tap n.
Figure2(b) shows the optical spectrum of the BEFL and Figure 2(c) shows the frequencyresponse of the MPF in which BEFL is used as optical source and 8 tap 2.Figure2. (a) Frequency response of MPF where solid line used for experimental anddashed line used for simulation. (b) Optical spectrum of BEFL before (blue) and after (green) the PSP. The spectral profile ofthe PSP is shown in red. III. Using Multimode laser diodeThe main topology for MPF used in 4 isas shown in figure 3.
It is mainly established multimode laser diode (MLD),optical isolator (OI), polarization controller (PC), mach zehnder intensitymodulator (MZ-IM), single mode standard fibre (SM-SF), photo diode (PD). Figure 3.Basic topology for MPF 3As per 4 frequency response of MPF isdirectly proportional to the spectrum of laser diode used. So for periodicityof the response MLD is important. To obtain good optical stability OI is usedbecause it avoids reflection of MLD. To control output power of MZ-IMpolarization controller is required. To give input electrical signal electricalsignal generator is used and this electrical signal is modulated on opticalcarrier signal.
After modulator, modulating signal is enter into SM-SF and thenthese optical signal converted into electrical signal using PD. Then outputsignal is analyse using electrical spectrum generator. In the frequency response of MPF centralfrequency of band-pass window is given as 4 is (1)And the bandwidth at 3-dB of theband-pass window is given by 4 (2)Where is optical bandwidth of the MLD. The MLD usedin these experiment 4 is (OKI-OL5200N-5) is as shown in figure 4.
Figure4. Spectrum of MLD 4 IV. ApplicationUsing set up shown in figure 3 we cantransmit wireless signal and TV signal. Here figure 5 shows transmission ofwireless signal of 0.915 GHz 5 and figure 6 shows transmission of TV signalof 67.25 MHz 4. Figure 5.
Proposed system to transmit a stable reference signal of 0.915 (GHz) through25.25 (km) of optical fiber 5Figure 6.Experiment set up to transmit a TV signal of 67.25 MHz through 20.
70 (km) ofoptical fiber. 4As per application we can select MLD andSM-SF. For transmission of wireless signal in 5 they select the MLD isoptically 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 parameterfrequency response is as shown in figure 7. In these case frequency range is0.
01-10 GHz and central frequency of ban-pass window is 2.31, 4.62, 6.86, and9.14 respectively. And bandwidth of the window is 647.9 MHz 5. As shown infigure 8 for transmission TV signal in 4 they select the MLD is optically describedby 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 responseis as shown in figure 8. In these case frequency range is 0.01-4 GHz andcentral frequency of band-pass window is 2.8 GHz.
And bandwidth of the windowis 543.70 MHz 4. Figure 7.Measured frequency response of MPF 5Figure 8.
Measured frequency response of MPF 4 V. ConclusionUsing BEFL, we analyze the MPF and itsfrequency response in which two band-pass window is getting in the frequencyrange of 0-5 GHz. Same way using different parameter of MLD and SM-SF we canget appropriate frequency response.
These parameters are FSR of optical source,dispersive parameter and length of fibre used. As per application we can decideparameter of MLD and SM-SF. Here two application is described one istransmission of wireless signal and another is transmission of TV signal.REFERENCE1 Thomas K.
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