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Optical Fiber Applications

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Nguyễn Gia Hào

Academic year: 2023

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Inquiries regarding the use of the book should be directed to the rights and permissions department of INTECHOPEN LIMITED (permissions@intechopen.com). As you know, one of the main applications of optical fibers is optical communications, which were initially inefficient.

Optical fibers

In these fibers, the modes of transmission are numerous and therefore the distances that these fibers can cover can be more than 50 times that of multimodal fibers. When comparing the transmission capacity of copper, which allows a few million pulses per second, versus more than 20 million pulses that can be transmitted in an optical fiber, it is possible to appreciate the great efficiency advantage.

Figure 3 shows a graphic comparison of the expected behavior in the two types  of the mentioned fibers; the way of sending information between the fibers can be  noted.
Figure 3 shows a graphic comparison of the expected behavior in the two types of the mentioned fibers; the way of sending information between the fibers can be noted.

Optical fiber transmission

Among the amplifiers doped with rare earth metals, those can be made with optical fiber doped with erbium and doped with ytterbium [10-12]. The optical fibers doped with erbium are most often used for the construction of this type of amplifiers, among other sensors and other applications [13-16].

Optical fiber applications

The review will begin with an overview of available material systems for active region laser emission in the 2μm spectral region. Basic static characteristics of the devices are discussed and operation in the 1.6-2.1μm spectral window is demonstrated.

Introduction

However, the transmission performance of SI-POF is hampered by strong intermodal dispersion and high optical attenuation. Fundamentals of WDM for Short Range Communication via POF2.1 Transmission Characteristics of 1mm PMMA SI-POF.

Fundamentals of WDM for short-range communication over POF 1 Transmission properties of 1 mm PMMA SI-POF

The first aim of this work is to further investigate these demultiplexing techniques for SI-POF experimentally. The contributions of the intrinsic loss mechanisms to the overall attenuation of SI-POF are also shown in Figure 3.

Demultiplexing employing thin-film interference filters

Data transmission techniques for increasing the channel capacity

According to Nyquist's theorem for two-level signaling, the maximum bit rate (in bits per second) for a noise-free channel of bandwidth B is 2B. If the data rate is increased further, the eye diagram of the received signal is partially or completely closed due to the combination of ISI and additional noise (introduced, eg, by the receiver's transimpedance amplifier). The output of the equalizer is obtained as the weighted sum of the delayed samples of the input signal as.

The BER performance of the system was estimated from the Q factor of the smoothed eye plot (Figure 6).

DMT: discrete multitone modulation

Simultaneous transmission of low-speed parallel currents reduces the impact of ISI. The principle of DMT transmission over an IM/DD optical channel is shown in Figure 7. The modulation of complex values ​​at N different subcarrier frequencies is based on the inverse fast Fourier transform (IFFT).

To obtain real-valued time-domain signal samples at the output of the IFFT block, a 2 N-point IFFE must be performed.

POF demultiplexer employing thin-film interference filters

Operating principle and measurement results for a four-channel demultiplexer By extending the channel count to four, it was possible to investigate two different

Principle of operation of a four-channel SI-POF demultiplexer with serial configuration (see enumeration in Figure 3). Non)adjacent channel isolation [dB] >30. Operating principle of a four-channel SI-POF demultiplexer with two-stage configuration (see enumeration in Figure 8). The separation of the individual wavelength channels was then performed within the second stage of the demultiplexer.

The practical realization was carried out with a 505 nm cutting long-pass dichroic mirror in the first stage of the demultiplexer.

Discussion

The beam radius was increased due to the beam divergence caused by the limited size of the source fiber [27]. If the effect of alignment inaccuracy, which is a parameter related to the particular setup arrangement, is neglected, all other effects that are inherent in the series setup would lead to the same basic behavior of the transfer function. An outstanding performance of that demultiplexer with IL between 3.19 and 5.66 dB (minimum overall IL of 16.87 dB) can be explained by a very precise alignment of the components.

The importance of this and of the other previously realized interference filter based SI-POF demultiplexers is that they enable the realization of POF WDM systems and investigation of their data-carrying capacity.

WDM transmission employing NRZ modulation

Experimental setup

The temperature of the mount's built-in temperature control element (TEC) was set to +15°C. Cooling to +10°C was used only for the OSRAM samples to ensure better stability of the optical output power. The TEC element temperature and bias current were controlled via a Thorlabs ITC8022 module.

In order to increase the efficiency of the coupling of the laser diode to the fiber, a coupling unit based on an xy-translator (0.25 mm pitch of set screws) was used.

Measurement results and discussion .1 Gb/s transmission over 10 m SI-POF

Considering the amplitude levels of the recorded eye diagrams and the low inter-channel crosstalk, it is not possible to assume a decrease in the SNR of the received signals if the laser diodes were modulated simultaneously. Due to the low impedance of laser diodes (typically 2-5 ohms), a serious impedance mismatch was present. By using a higher power of the modulation signals, however, the mismatch could be compensated.

Considering the amplitude levels of the recorded eye diagrams and the low interchannel crosstalk, as in the previous experiment, no power penalty due to crosstalk could be assumed if the laser diodes were modulated simultaneously.

WDM transmission employing NRZ modulation and FFE equalization This subchapter shows the improved experimental setup and gives the mea-

To realize the bundle, an Asahi KASEI DB-400 PMMA SI-POF with 400 μm cladding diameter and NA = 0.5 was used. As illustrated in Figure 18, an FC connector sleeve was used to assemble and align the bundle and input to the SI-POF link, forming the multiplexing interface. Thereby, only a small time window (2% of the unit interval) in the center of the equalized eye diagram was taken into account.

Thereby, six FFE taps were used with the tap delay equal to half the corresponding bit period in each of the channels.

Conclusions

TS 105 175-1—V1.1.1—Access, Terminal, Transmission and Multiplexing (ATTM); Plastic optical fiber system specifications for 100 Mbit/s and 1 Gbit/s. 4] Access, Terminal, Transmission and Multiplexing (ATTM); Plastic optical fibers; Part 1: Plastic optical fiber system specifications for 100 Mbit/s and 1 Gbit/s; Sub-Part 2: 1 Gbit/s and 100 Mbit/s Physical layer for plastic optical fibres, ETSI Technical. Development status of a four-channel CWDM system for multi-Gbit/s data links over SI-POF.

Development status of a four-channel CWDM system for Multi-Gbit/s internal data communication via SI-POF.

The roadmap toward elastic optical networks

Moreover, providing additional capacity in this way is very inefficient in terms of the spectrum resources consumed. Despite the increasing popularity of elastic optical networks, very little work has focused on elastic node architectures. These parameters are interdependent and their relative time evolution, together with the associated network economics, will dictate the exact network development assuming the maturity of available technology.

The resulting spectral savings are achieved by taking advantage of spectral resources that were not yet fully utilized, thus bringing about an increase in network capacity [25].

Optical switching paradigms

Switching technology

To fully realize the vision of elastic optical network, network operators have migrated to flexible transport technology solutions capable of supporting network distance flexibility. In this way, elastic optical road networks accommodate a wide range of traffic in a highly spectrally efficient manner [26]. As mentioned, elastic optical communication is based on the principle that the fiber's bandwidth can be dynamically divided into resizable spectrum slots.

The combination of advanced wireless spectrum switching devices and fast time switching enables the provision of a wide range of optical bandwidth granularities [6]; however, they do not have a large number of ports, which makes them incompatible for connecting devices in an elastic fiber hub.

Need for elastic optical node in optical fiber communication

The optical cross-connect architecture consists of subsystems such as Quad Semiconductor Optical Amplifier-Mach-Zehnder interferometer, 200 ms LCoS-based SSS [43], wavelength/waveband AWG, (De)-Multiplexer, optical power couplers/dividers and EDFA used interconroe-69 mechanical systems. link. It also significantly improves the efficiency and elasticity of the optical node and provides support for current and future data rates with transparent facilities with low power consumption. All the traffic to node is routed over a dark fiber link, and performances are evaluated by means of BER measurements [7].

Key functional building blocks for next generation elastic optical network: wavelength conversion, format conversion and multicasting

The service node provides the required real-time all-optical processing [44] functionalities, arbitrary spectrum switching and time domain sub-wavelength switching [45]. Key functional building blocks for next-generation elastic optical network: wavelength conversion, format conversion, and multicasting. Importantly, conversion of all-optical modulation formats is likely to be used for future all-optical networks to add the optical network flexibility [50, 51].

Therefore, a critical requirement will be the transparent interconnection of these different network islands, which should be done by all-optical means at the network gateways [52].

All optical converters

Cross gain modulation (XGM)

In its general form, the working principle of the technique is that an optical input signal to be wavelength converted is used to saturate the gain of an active nonlinear element, thereby modulating a continuous wave (CW) signal (pump) at the desired output wavelength as shown in Figure 7. Some indicative examples include the work presented in [61] where a 0.5-pen 1.2 d conversion is used for 1. alt. XGM WCs are attractive because of their simplicity and high conversion efficiency, and the conversion can be made independent of the polarization of the incoming signal.

The XGM converter has a number of shortcomings, such as (bitstream) data polarity inversion and the relatively large chirp of the output signal due to the large gain modulation.

Cross phase modulation (XPM)

Finally, in addition to wavelength conversion, XGM has been used for many functions, such as: format conversion [64], multicasting [65]. Nevertheless, due to carrier recovery time, the working bit rate of the MZ is limited, as are the XGM ports. This configuration has been used in a number of different signal processing applications such as demultiplexing [81], regeneration [82], add-and-drop multiplexing [83], regenerative add-and-drop multiplexing [84], and format and wavelength conversion [85].

Due to the inherently ultrafast response of the Kerr nonlinearity, the NOLM is able to perform a number of fast bit-level processes, e.g. 640 to 10 Gb/s demultiplexing [88], regeneration [89], simultaneous 10 Gb/s wavelength and regeneration conversion and [90-clock] extraction and [90-clock].

Wave mixing based: four wave mixing (FWM)

A schematic of the FWM process, which takes place in nonlinear media, is shown in Figure 10. The use of an assisted beam has been suggested for increasing the efficiency of FWM in [105, 106]. FWM effect in spectral domain after signal propagation and two pumps in DSF fiber [27].

FWM is a very promising technique, but due to the complexity of the configuration for polarization insensitive operation or wide tuning, it is likely to be used only for converters operating at 100 Gb/s and above.

All optical signal processing functionalities survey

Conclusion

Cross-sectional distribution of the refractive index of a bent GR-IN optical fiber when the incident light vibrates (a) parallel and (b) perpendicular to the fiber axis. c) Distribution of the birefringent section, R= 8 mm. Calculated and experimental phase differences of an optical fiber bowtie when the incident light vibrates (a) parallel and (b) perpendicular to the fiber axis. In these models, the refraction of the light beam traversing the fiber was taken into account.

Especially for the Taper 2 with a parabola-1 shape, we obtain an improvement of the temperature sensitivity in the fiber amplifier. The signal is calculated at the end of the tapered fiber (3 m) according to the scheme of Figure 1. Optical scheme of the primary converter: 1, radiation source (LED); 2, fiber optic coupler; 3, location of optical signal distribution; 4, temperature sensitive element; 5, the first photodiode (FD1); and 6, the second photodiode (FD2).

Figure 14a shows a set of five phase shifted interferograms for the bent GR-IN optical fiber with bending radius R = 8 mm when the incident light was vibrating parallel to the fier ’ s axis
Figure 14a shows a set of five phase shifted interferograms for the bent GR-IN optical fiber with bending radius R = 8 mm when the incident light was vibrating parallel to the fier ’ s axis

Hình ảnh

Figure 3 shows a graphic comparison of the expected behavior in the two types  of the mentioned fibers; the way of sending information between the fibers can be  noted.
Figure 14a shows a set of five phase shifted interferograms for the bent GR-IN optical fiber with bending radius R = 8 mm when the incident light was vibrating parallel to the fier ’ s axis
Figure 4 shows a picture of one of the crystal GaP:Zn. This plate was used in our optical studies.

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- When the fiber and particle volume fraction ratio increase the one-direction compression resistance of the plate increase, the effect of fiber on the plate's buckling