Pertumbuhan layanan telekomunikasi terus berkembang saat ini maupun masa yang akan datang. Seiring dengan bertambahnya kebutuhan di bidang telekomunikasi tentunya membutuhkan sarana telekomunikasi yang memadahi. Hal ini disadari oleh PT. Telkom Indonesia dengan menyediakan layanan dengan produk dan kualitas jaringan yang berkualitas. Untuk itu perlu diadakan evaluasi terhadap kualitas jaringanTerutama pada jaringan backbone, penggunaan jaringan ini digunakan agar suatu layanan komunikasi yang memadai dapat terselenggara. Salah
satu faktor terpenting adalah sistem transmisi yang tepat, dalam hal ini jaringan backbone Alacatel Northern Route Netre Jabar Wilayah Bandung . Dengan melakukan evaluasi, diharapkan dapat memenuhi kebutuhan teknologi telekomunikasi, sehingga akan menciptakan high quality infrastructure network Infratel yang ada di Netre Jabar Wilayah Bandung .
Coherent Homodyne Communication System
What is coherent optics?
At its most basic, coherent optical transmission is a technique that uses modulation of the amplitude and phase of the light, as well as transmission across two polarizations, to enable the transport of considerably more information through a fiber optic cable. Using digital signal processing at both the transmitter and receiver, coherent optics also offers higher bit-rates, greater degrees of flexibility, simpler photonic line systems, and better optical performance.
Homodyne Detection
Homodyne detection is a method of extracting information encoded as modulation of the phase and frequency of an oscillating signal, by comparing that signal with a standard oscillation that would be identical to the signal if it carried null information. “Homodyne” signifies a single frequency, in contrast to the dual frequencies employed in heterodyne detection. When applied to processing of the reflected signal in remote sensing for topography, homodyne detection lacks the ability of heterodyne detection to determine the size of a static discontinuity in elevation between two locations. Homodyne detection is more readily applicable to velocity sensing.
Homodyne Detection in Optic
In optical interferometry, homodyne signifies that the reference radiation (the local oscillator) is derived from the same source as the signal before the modulating process. For example, in a laser scattering measurement, the laser beam is split into two parts. One is the local oscillator and the other is sent to the system to be probed. The scattered light is then mixed with the local oscillator on the detector. This arrangement has the advantage of being insensitive to fluctuations in the frequency of the laser. Usually the scattered beam will be weak, in which case the (nearly) steady component of the detector output is a good measure of the instantaneous local oscillator intensity and therefore can be used to compensate for any fluctuations in the intensity of the laser.
Key Benefits
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- Noise reduction to shot noise limit As with any small signal amplification, it is most desirable to get gain as close as possible to the initial point of the signal interception: moving the gain ahead of any signal processing reduces the additive contributions of effects like resistor Johnson-Nyquist noise, or electrical noises in active circuits. In optical heterodyne detection, the mixing-gain happens directly in the physics of the initial photon absorption event, making this ideal. Additionally, to a first approximation, absorption is perfectly quadratic, in contrast to RF detection by a diode non-linearity.
- Mapping optical frequencies to electronic frequencies allows sensitive measurements The difference frequency linewidth can be much smaller than the optical linewidth of the signal and LO signal, provided the two are mutually coherent. Thus small shifts in optical signal center-frequency can be measured: For example, Doppler lidar systems can discriminate wind velocities with a resolution better than 1 meter per second, which is less than a part in a billion Doppler shift in the optical frequency. Likewise small coherent phase shifts can be measured even for nominally incoherent broadband light, allowing optical coherence tomography to image micrometer-sized features. Because of this, an electronic filter can define an effective optical frequency bandpass that is narrower than any realizable wavelength filter operating on the light itself, and thereby enable background light rejection and hence the detection of weak signals.
TECHNOLOGY GPON
WHAT IS GPON ?
GPON is one of the technologies developed by ITU-T via G.984 and until now competes with GEPON (Gigabit Ethernet PON), namely the IEEE PON version based on Ethernet technology. What is characteristic of this technology compared to other optical technologies such as SDH is the technique of traffic distribution carried out passively. From the central to the direction of the subscriber will be distributed using passive splitters
WORKING PRINCIPLES OF GPON
GPON is an FTTx technology that can send information to customers using optical cables. The working principle of GPON, when data or signals are sent from OLT, then there is a section called the splitter which functions to allow a single optical fiber to send to various ONUs, for the ONU itself will provide data and signals that the customer wants. In principle, PON is a point to multipoint system, which uses the splitter as a network divider
ADVANTAGE OF GPON
- Supports triple play applications (voice, data and video) on servicesFTTx is done through one fiber optic core.
- Can divide bandwidth up to 32 ONT.
- GPON reduces the use of many cables and equipment at headquarters if compared to point to point architecture. Only one optical port in the center office (replacing multiple ports).
- Bandwidth allocation can be set.
- Maintenance costs are cheap because they use passive components.
DISADVANTAGE OF GPON
- Complex layering model
- More expensive than GEPON
- Upstream bandwidth is limited to 622 Mbps
GROUP 15
Phaksi Ghagono Awang Murti (1101154124)
I Gede Aditya Pratama (1101154215)
Wildan Maulani (1101154358)
WAVELENGTH SELECTIVE SWITCHING (WSS)
What is Wavelength Selective Switching ?
Wavelength selective switching (wss)
WSS stands for Wavelength Selective Switch.
WSS has become the central heart of modern DWDM reconfigurable Agile Optical Network (AOC).
WSS is a tool which is used to dynamically route, block and attenuate all DWDM wavelengths within a network node.
This Following Figure Shows WSS Functionality
This figure shows that a WSS consists of a single common optical port and N opposing multi-wavelength ports where each DWDM wavelength input from the common port can be switched (routed) to any one of the N multi-wavelength ports, independent of how all other wavelength channels are routed.
This wavelength switching (routing) process can be dynamically changed through a electronic communication control interface on the WSS. So in essence, WSS switches DWDM channels or wavelengths.
How Does WSS Work ?
A. 1X2 Configuration
This figure shows that a WSS consists of a single common optical port and N opposing multi-wavelength ports where each DWDM wavelength input from the common port can be switched (routed) to any one of the N multi-wavelength ports, independent of how all other wavelength channels are routed.
This wavelength switching (routing) process can be dynamically changed through a electronic communication control interface on the WSS. So in essence, WSS switches DWDM channels or wavelengths.
B. 1XN Wavelegth Selective Switch
The 1XN switch can be considered as a generalization of the 1×2 switch. Because every wavelength in the 1XN switch can be switched to any one of the N output ports, this switch can be used in a fully flexible OADM (Optical Add Drop Multiplexer) with multiple add/drop fiber ports, each of which carries single or multiple wavelengths.
1XN switches can be cascaded to form larger architectures, and NxN wavelength selective matrix can be built by interconnecting back-to-back 1XN switches.
In the 1xN switch design, it uses an additional lens in Fourier transform configuration to perform a space to angle conversion in the first stage of the switch. Also the 1xN switch will require tilt mirrors with N different tilt angles. These are usually implemented as analog mirrors.
Optical Design of The 1xN WSS
Here is how the design works.
- The common input fiber enters the switch at point A where light is collimated by a microlens.
- The following lens image the collimated beam on the diffraction grating at point C.
- The wavelength dispersed beams fall then onto the MEMS device plane D
- On MEMS device plane D, the beams are reflected with certain tilt angle depending on micromirrors’ setting.
- All reflected beams are focused on point B again, where the angle to space conversion section will image the beam on the output fiber. Each output corresponds to a specific tilt angle of the micromirrors.
GROUP 15
Phaksi Ghagono Awang Murti (1101154124)
I Gede Aditya Pratama (1101154215)
Wildan Maulani (1101154358)
MODULATOR MACH ZEHNDER
Modulator Mach Zehnder
Mach Zehnder modulator is one of the integrated optical devices and can support a fiber optic network to be more reliable. Mach-Zehnder modulator is an external optical modulator that uses electro-optical effects that conventionally use modulating signals in the form of digital signals (NRZ, RZ, etc.). The device has a large bandwidth capacity. The device has a modulation speed up to giga order. The advantage of the Mach Zehnder modulator is that it utilizes superposition so that the output signal power becomes larger and allows remote communication with a small BER level.
Mach Zehnder Modulator Function
Mach Zehnder modulator is an electro-optical device used to modulate wave amplitude. As the name implies the modulator is a function of laying out information signals in the form of pulses of light into the carrier signal (carrier) so that it can be transmitted to the destination.
How to Work Mach Zehnder Modulator
A Mach Zehnder modulator consists of two Y-branches placed opposite and separated by distance. Arm both spaced and controlled by external voltage. The first Y branch functions to propagate the incoming light wave, then manipulated by the arm spacing, and out of the Y branch combines the light of the two arms. Mach Zehnder modulator is an external modulator where the information signal and carrier signal are outside the device then the modulation process is on a separate device. When the light is recombined again, the two waves are interfering with each other. If two waves are in phase then a constructive disturbance occurs and the output is ON. If it comes out of phase, destructive interference will occur and the wave will cancel each other, then the output is OFF. For the ON light is represented by 1 binary and to OFF the light is represented by binary 0.
Mach Zehnder Modulator Performance Parameters
According to the nature of the material used, the modulator is divided into two groups: absorbent modulator and bias modulator. In the absorption modulator the material absorption coefficient changes, in the modulator the bias of the material refractive index changes. The absorption coefficient of the material in the modulator can be manipulated by the Franz-Keldysh effect, the Stark Quantum-limited effect, excitonic absorption, changes in the Fermi level, or changes in the free carrier concentration. Usually, if some effects appear together, the modulator is called the electro-absorptive modulator. The bias modulator most often utilizes the electro-optical effect. Some modulators utilize the accousto-optic effect or magneto-optical effect or take advantage of changes in polarization in liquid crystals.
GROUP 15
Phaksi Ghagono Awang Murti (1101154124)
I Gede Aditya Pratama (1101154215)
Wildan Maulani (1101154358)
ARTIKEL dan JURNAL
ARTIKEL
Pengertian Resonansi Bunyi
Ketika ada suara petir seringkali kaca jendela di rumah ikut bergetar. Mengapa hal ini terjadi ?bergetarnya kaca jendela ketika terdengar suara petir terjadinya karena adanya peristiwa resonansi bunyi. nah apa ituresonansi ? untuk memahami konsep resonansi simak uraian berikut !
Resonansi adalah peristiwa ikut bergetarnya suatu benda akibat benda lain yang bergetar karena keduanya memiliki frekuensi yang sama atau memiliki frekuensi yang merupakan bilangan bulat dari frekuensi salah satu benda bergetar. Resonansi bunyi pada kolom udara dimanfaatkan untuk menghasilkan bunyi pada alat musik. Alat- alat musik memiliki lubang udara sehingga terjadi resonansi udara dan menghasilkan suara yang merdu.
Misalnya : bunyi merdu pada gitar dihasilkan oleh resonansi anatara dawai dan kotak resonansi. Ketika gitar di petik udara di dalam kotk resonansi bergetar dengan frekuensi yang sama dengan frekuensi dawai. Udara yang berada di dalam kendang juga ikut bergetar ketika kendang dipukul. Jika tidak ada kolom udara pada alat musik kita tidak dapat mendengar merdunya suara musik.
Untuk memahami bagaimana proses resonansi kita perhatikan dua buah garputala yang beresonansi seperti pada gambar.
resonansi bunyi pada garputala |
Apabila salah satu garputala kita pukul, maka garputala akan bergetar. hal ini menyebabkan garpula lainnya juga ikut bergetar karena frekuensi keduanya sama. Frekuensi bunyi pada garputaladipengaruhi oleh bentuk garputala, bahan garputala dan besar kecilnya garputala
Resonansi pada kolom udara
Contoh peristiwa resonansi lainnya ketika digetarkan sebuah garputala diatas kolom udara yang berada di atas permukaan air menyebabkanmolekul udara di dalam kolom ikut bergetar, seperti yang ditujukkan pada gambar :
peristiwa resonansi kolom pada adara |
Adapun Syarat untuk terjadinya resonansi bunyi tpada kolom uadara ialah terbentuk simpul gelombang pada permukaan air dan ujung tabung bagian atas sebagai perut gelombang.
Kolom udara berfungsi sebagai tabung resonator. Peristiwa resonansi dimanfaatkan untuk mengukur kecepatan perambatan bunyi di udara. Adapun syarat terjadinya resonansi. panjang kolom udara yang diperlukan agar terjadi resonansi sepanjang l = (2n-1)¼λ, dengan n = 1, 2, 3, . . .
Kita dapat mendengar resonansi yang berurutan jika resonansi pertama dengan resonansi berikutnya berjarak Δl = ½ λ.
Apabila frekuensi (f) sebuah garputala dan panjang gelombang bunyi (λ) diketahui, kita dapat menentukan cepat rambat bunyi diudara dengan persamaan :
v= λ x f
Selain bermanfaat, resonansi juga dapat merugikan. Misalnya :
1. Resonansi dapat merobohkan jembatan gantung apabila frekuensi alami jembatan sama dengan frekuensi langkahkaki sekelompok orang yang berjalan diatas jembatan. Hal ini menyebabkan jembatn akan berayun yang berakibat runtuhnya jembatan gantung tersebut.
2. Resonansi dapat memecahakan kaca jendela jika ada suara petir yang sangat keras. Hal ini karena frekuensi alami kaca sama dengan frekuensi petir sehingga kaca akan ikut bergetar ketika ada petir.
Sumber :
http://seputarpendidikan003.blogspot.co.id/2014/12/pengertian-resonansi-bunyi.html
JURNAL
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