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Jan 10 2018

Comprehensive Knowledge of Passive Devices

Warm hints: The word in this article is about 3800 and reading time is about 20 minutes.


Microwave RF devices are divided into two categories: passive and active. The standard  between active and passive devices are to distinguish whether the equivalent circuit model of the device contains power supply (voltage source or current source). If there is no power in the equivalent circuit model of the device, the device is called passive device. They mainly includes resistors, capacitors, inductors, converters, gradients, matching networks, resonators, filters, mixers and switches. This paper will mainly introduces some basic knowledge of passive devices such as types of opticla passive components; passive device definition; active and passive components; some famous semiconductor manufacturers in the world and etc.

Article coreComprehensive Knowledge of Passive DevicesComponentResistors, inductors, and capacitances
English namePassive Devices


NatureMicrowave radiofrequency devicesIncludeResistance, capacitance, inductance, converter



I.What is Passive Devices

5.Optical switch

II.Optical Passive Components

6.Wavelength division multiplexer

1. Fiber optic active connector

7.Light junction box, optical wiring box, light terminal box

2.Optical splitter

III.Ten famous semiconductor manufacturers in the world

3.Optical attenuator

IV.Active and Passive components

4.Optical isolator

V.Types of passive components


I.What is Passive Devices

Microwave RF devices are divided into two categories: passive and active. The standard  between active and passive devices are to distinguish whether the equivalent circuit model of the device contains power supply (voltage source or current source). If there is no power in the equivalent circuit model of the device, the device is called passive device. They mainly includes resistors, capacitors, inductors, converters, gradients, matching networks, resonators, filters, mixers and switches. Ok,let's see a video at first as usual.

This video is about Passive components--Lecture Series on Basic Electrical Technology teached by 

Professor  L.Umanand, Principal Research Scientist, Power Electronics Group, CEDT, IISC Bangalore 

II.Optical Passive Components

Optical passive components is an important part of optical fiber communication equipment. It is a kind of optical components, various test methods to calculate the formula and process of the basic law and abide by the principle of optical ray theory and electromagnetic wave theory, the technology index, variety, and is closely related to fiber optics, integrated optics; therefore it is essentially different from the electrical passive devices. In fiber cable TV, it plays the role of connection, distribution, isolation, filtering and so on. There are many kinds of passive devices, which are commonly used as optical splitter, optical attenuator, optical isolator, connector, jump line, optical switch. Let’s learn them one by one.

1. Fiber optic active connector

Fiber optic active connector--Comprehensive Knowledge of Passive Devices

Optical fiber active connector is a passive optical device for active connection between optical fibers. It also has functions of connecting optical fiber to active devices, optical fibers and other passive devices, optical fibers and systems and meters. Active connectors are developing along with the development of optical communication. Now, there are many kinds of products that are complete and varied. It is one of the most indispensable and widely applied basic components in the field of optical fiber application. Although optical fiber cable connectors are different in structure and variety, their functions can be divided into the following parts: connector plugs, optical fiber jumpers, converters, converters and so on. These components can be used individually as devices, and they can also be used together to become components. In fact, an active connector is used to refer to two connector plugs plus a converter.

2.Optical splitter

Optical splitter--Comprehensive Knowledge of Passive Devices

As with the coaxial cable transmission system, optical network system also needs to be an optical signal coupling, branch and distribution, which requires the optical splitter to realize optical splitter is one of the most important passive devices in fiber links, with multiple input and multiple output end of the optical fiber junction devices, commonly used M * N to represent a splitter with M input and N output. The optical splitters used in the optical fiber CATV system are generally 1 * 2, 1 * 3 and 1 * N optical splitters composed of them. We need to learn it according two steps.

 (1)The principle of light splitter

According to the principle of optical splitter and fiber type can be divided into two kinds of planar waveguide, optical fiber fused products are of two or more fiber side weld formed; optical waveguide is the optical element type products, using lithography, optical waveguide formed on a semiconductor substrate or medium, implementation of branch distribution function. These two types of light splitting principles are similar. They achieve different size branches by changing the evanescent field coupling (coupling degree, coupling length) and changing the fiber radius of optical fibers. Otherwise, multiple optical signals can be combined into one signal called synthesizer. Fused tapered fiber coupler is simple, cheap, and easy to connect with external optical fibers. It also has the advantages of resistance to mechanical vibration and temperature changes. Now it has become the mainstream manufacturing technology in the market.

FBT is two (or two) to remove the fiber coating by a certain method depend on the high temperature heating, melting, and stretching to both sides, eventually forming a special waveguide structure of double cone form in the heating zone, by controlling the fiber twist angle and tensile length can be divided into light the proportion of different. Finally, the taper area is solidified with the solidified adhesive on the quartz substrate and inserted into the stainless steel tube. This is the optical splitter. The production process for curing adhesive coefficient of thermal expansion and quartz substrate, stainless steel tube is not consistent, temperature changes in the environment, thermal expansion and contraction of the degree of inconsistency, this situation can easily lead to optical splitter damage, especially the optical branch located in the field even more, it is also easy to damage the main optical branch the reason. For the splitter production more channels can be composed of a plurality of two splitters.

(2) Common technical indexes of optical splitter

  • (a) insertion loss. The insertion loss of optical splitter refers to each output relative to input the number of my dB light loss, the mathematical expression of Ai=-10lgPouti/Pin, Ai is the first I output port of the insertion loss of optical power is Pouti; the I output port of the optical power is Pin; the input value.

  • (b) additional loss. The additional loss is defined as the DB number of the total optical power of all output ports relative to the loss of the input light power. It is worth mentioning that for fiber coupler, the additional loss is the index reflecting the quality of device manufacturing process, reflecting the inherent loss of device fabrication process. The smaller the loss, the better is the evaluation index for making quality. The insertion loss only indicates the output power of each output port, not only the factor of inherent loss, but also the influence of the light splitting ratio. Therefore, the difference of insertion loss between different fiber couplers does not reflect the quality of the device.

  • (c) the ratio of light splitting.The splitting ratio is defined as the ratio of output power splitter of each output port, in the system application, the splitting ratio is determined according to the optical power required for optical nodes to the actual system, determine the appropriate splitting ratio (except the average distribution), optical splitter splitting ratio and transmission of light the wavelength, such as an optical branching transmission in 1.31 micron light when two output light is 50:50; in the transmission of 1.5 m light, it becomes 70:30 (the reason why this happens, because the optical splitter has a certain bandwidth, the splitting ratio basically unchanged when transmitting signal band width). So when you make a light divider, you must mark the wavelength. (d) the degree of isolation. Isolation is the ability to isolate the light signals from other optical paths by a light path of the optical splitter. In the above indicators, the isolation degree is more significant for optical splitter. In practical systems, devices often need isolation above 40dB, otherwise, the performance of the whole system will be affected. The optical splitter stability is also an important indicator of the stability refers to the change in the outside temperature, other devices working condition changes, light splitter ratio and other performance indicators should remain unchanged, the technological level of the actual stability glazing splitter depends entirely on the manufacturer, different manufacturers the product quality gap is quite big.

3.Optical attenuator

Optical attenuator--Comprehensive Knowledge of Passive Devices

Optical attenuator is a very important fiber optical passive device. It is an indispensable device in the optical fiber CATV. Up to now, the market has formed four series of fixed type, step adjustable, continuous adjustable and intelligent optical attenuator.

(1).The attenuation principle of the attenuator. 

There are many types of optical attenuators, and different types of attenuators use different working principles.

  • (a).displacement optical attenuator.As we all know, when two segments of optical fiber are connected, it is necessary to achieve a fairly high middle precision in order to transmit the light signal in a small loss. In turn, if the accuracy of the pair of optical fibers is adjusted properly, the attenuation can be controlled. Based on this principle, the optical fiber attenuator is deliberately misplaced when the optical fiber is butted. So that the loss of light energy can be achieved, so as to control the decrement. Displacement optical attenuators can be divided into two types: lateral displacement optical attenuator and axial displacement optical attenuator. Transverse displacement type optical attenuator is a traditional way, because the magnitude of the lateral displacement parameter is at the micron level, it is generally not to make variable attenuator is only used for making fixed attenuator, and the welding or bonding method, until now it is still a large, the utility model has the advantages of high return loss generally, more than 60dB. As long as the axial displacement optical attenuator is designed by mechanical method, the two fibers can be pulled in a certain distance, and the purpose of attenuation can be achieved. This principle is mainly used for the fabrication of fixed optical attenuators and small variable optical attenuators.

  • (b)Thin film optical attenuator.The attenuator makes use of the principle that light is related to the thickness of the film on the surface of a metal film. A fixed optical attenuator is made if the thickness of the coated metal film on the glass substrate is fixed. If a series of thin metal thin glass substrates with different thickness are inserted vertically into the optical fiber, the intensity of the reflected light can be changed by inserting different thickness of metal film into the optical path, so that different attenuation can be obtained, and variable attenuators can be made.

  • (c)The attenuator type optical attenuator.

 The attenuation type optical attenuator directly absorbs the absorption characteristic attenuation piece on the end face or optical path of the optical fiber to achieve the purpose of attenuating the optical signal. This method can not only be used for making the fixed optical attenuator, but also for making variable optical attenuator.

(2)Performance index of optical attenuator

  • (a)Attenuation and insertion loss. The attenuation and the insertion loss is an important index of optical attenuator, attenuation index of fixed optical attenuator is actually the insertion loss, and in addition to variable attenuator attenuation, and separate insertion loss index, the insertion loss of the variable attenuator of high quality in the 1.0dB next to the general average of the index is less than the variable attenuator you can use 2.5dB. When the adjustable attenuator is selected, the smaller the insertion loss is, the better. But this is bound to be involved in the price.

  • (b)The attenuation accuracy of the optical attenuator. Attenuation accuracy is an important index of optical attenuator. Usually the attenuation accuracy of the mechanical adjustable optical attenuator is about 0.1 times of its attenuation. The size of the machine depends on the precision of the mechanical components. The attenuating precision of the fixed optical attenuator is very high. The higher the attenuation precision, the higher the price.

  • (c)Echo loss. An important indicator of the performance of the system in the optical device parameters is the return loss. The effect of return light on the optical network system is well known. The return loss of the optical attenuator is the ratio of the light energy incident to the optical attenuator and the light energy reflected along the incident light path in the attenuator. The return loss of the high performance optical attenuator is above 45dB. In fact, due process, the actual return loss from the theoretical value of the attenuator is still a certain gap to reduce the line return loss, high return loss must be used in the corresponding attenuator circuit, but also for optical attenuator with a wider range of temperature and frequency range.

4.Optical isolator

Optical isolator--Comprehensive Knowledge of Passive Devices

An optical isolator is a non reciprocal optical element that allows only a beam to pass through one direction and has a strong blocking effect on the reflected light. In the CATV optical transmission system, the optical fiber connector, optical fiber connector, optical element and Rayleigh scattering effect of fiber itself, there is always a reflection of light, have a detrimental effect on the performance of the system, so we must adopt optical isolator to eliminate the influence of reflection wave, the light reflection machine, optical amplifiers are installed optical isolator, isolaterconsists polarizer, polarizer rotator and three parts. Polarizer is an optical device. When the beam is incident on it, the output beam becomes a linearly polarized light in a certain direction, which is the polarization axis of polarizer. The polarizer can not be passed when the polarization direction of the incident light is perpendicular to the polarizer's polarization axis, so the polarizer can be used as a detector. The optical rotator material and set out in the form of permanent magnets, magnetic optical effect by the polarization direction of the light through it in a certain degree of rotation.

The working principle of optical isolator for polarizing axis polarizer and polarizer is 45o, when the incident light through the polarizer, was turned into a linearly polarized light, then the rotator of the polarization plane rotation is 45o, consistent with the polarization direction of the polarizer, and the optical signal by optical isolator and smooth into the light path. If there is a reflection light, the reflected light passes through the polarizer and the polarizer, and the polarization direction is perpendicular to the polarization direction of the polarizer and can not pass through the polarizer, so as to achieve the purpose of isolating the reflected light. The loss of each stage optical isolator to the reflected light is as high as 35dB.

The performance requirements of the optical isolator in the CATV system are: low forward loss, high reverse isolation, high echo loss, small device volume and good environmental performance. Because the optical isolator is more valuable, it is generally used in light sources, and it is not used in optical fiber lines. So it is not unnecessary, but from cost considerations. If the optical isolator is cheap and the insertion loss is small, it can be used in the line to improve the performance of the system.

5.Optical switch

Optical switch--Comprehensive Knowledge of Passive Devices

Optical switch is a kind of optical control device, optical switch plays a role in the optical fiber transmission network and optical switching system, which is controlled by microcomputer light exchange, distribution information between the terminal and the center of the exchange and intelligent; in the light of ordinary transmission system, can to switch between the main and backup light path, can be used for testing and sensing network of optical fiber optical fiber and optical device, the optical fiber transmission system, working measuring instrument or sensor system is stable and reliable, easy to use.

In CATV optical networks, in order to ensure uninterrupted operation of cable television system, should be equipped with a backup optical transmitter, optical transmitter when working out the fault, using optical switch can be in a very short time (less than 1ms) backup optical transmitter access system, ensure the normal work.

According to its working principle, optical switch can be divided into two types: mechanical and non mechanical. The mechanical switch is changed by optical fiber or optical element. The optical switch in the market is generally mechanical. Its advantage is low insertion loss, generally less than 1.5dB. The isolation is high, generally larger than 45dB, and is independent of polarization and wavelength. Non mechanical optical switch on the electro-optic effect, magneto-optical effect, acousto-optic effect and thermo optic effect to change the refractive index of waveguide, the optical path change, which is a new technology, the advantage of this type of switch is short switching time, small volume, convenient for optical integration or photoelectric integration; the deficiency is the insertion loss a large, low degree of isolation.

6.Wavelength division multiplexer

Wavelength division multiplexer--Comprehensive Knowledge of Passive Devices

In a fiber at the same time the transmitted light signal communication several different wavelengths of the wavelength division multiplexing, WDM technique is used, as long as a small increase in the wave, wave equipment between the transmitter and receiver can greatly increase the transmission capacity of optical fiber, improve economic efficiency. For the already laid optical fiber cable, using the wavelength division multiplexing technology, it can also realize multichannel transmission, and play the role of reducing the cost and expanding the capacity. Wavelength division multiplexer plays the role of combination and partial wave in optical path. It convers optical signals of different wavelengths into one optical fiber to transmit to the receiving end, and then redivides the optical signals transmitted by optical fibers. According to the splitting principle, wavelength division multiplexers can be divided into three types: Branch mirror, interference model and diffraction grating. Most of the products in the market are diffraction grating. The main indicators of WDM with insertion loss, crosstalk loss, wavelength interval and the number of channels etc.. Insertion loss refers to the optical power loss due to the use of a wavelength division multiplexer, usually around 1 - 5dB. The crosstalk loss indicates the degree of division of the wavelength division multiplexer to each wavelength. Crosstalk attenuation as possible, should be more than 20dB.

7.Light junction box, optical wiring box, light terminal box

Light junction box, optical wiring box, light terminal box--Comprehensive Knowledge of Passive Devices

The length of each cable is mostly at 2. Under 5KM, it is necessary to connect the cable when connecting the long distance fiber cable. In order to ensure the connection strength and use in various environment conditions, the connection box should be pressed. The light box has joint sealing and waterproof function, it can be horizontally mounted, can be installed vertically. In order to ensure the strength of the connection, a steel wire is used to reinforce the cable between a section of the cable, and then each splicing fiber is arranged in a layered plate. A cable output, select the 1*1 joint box, if it is a cable input, N fiber cable output, select the 1*N joint box. When the number of optical cable cores is more than 16 pairs, the ordering needs to explain how many core cables are needed to increase the internal fiber heat shrinkable casing and fiber bracket.


III.Ten famous semiconductor manufacturers in the world



Fairchild Semiconductor

Global supplier of high performance semiconductor products for electronics industry.

Dynex Semiconductor

Manufacturer of power semiconductors, IGBTs, SCRs, GTO Thyristors, fast recovery and rectifier diodes, SCR/Diode modules, power assemblies, SAW filters and SOS ICs.

Analog Devices

HiHigh performance signal processing solutions.

Avago Technologies

Manufacturers and suppliers of semiconductors analog, mixed-signal and optoelectronic components and subsystems.


Design and manufacture advanced semiconductors.

AMI Semiconductor

Manufacturers of semiconductor and integrated circuit devices.

Advanced Semiconductor Engineering

The ASE Group is the world’s largest provider of independent semiconductor manufacturing services in assembly and test.

Renesas Technology

Semiconductor, microcomputers, logic and analog devices, discrete devices and memory products.

ON Semiconductor

Supplies a broad portfolio of semiconductors and integrated circuit devices.

This table is about Ten famous semiconductor manufacturers in the world


IV.Active and Passive components

In a simple way, a device that requires a source is called an active device, and a device that does not need a source is a passive device. Active devices are generally used for signal amplification, transformation, and so on. Passive devices are used for signal transmission, or "signal amplification" by directivity. The capacity, resistance and sense are passive devices, and IC and modules are all active devices. (the popular saying is that it needs power to show its characteristics is active components, such as triode. A passive component that can display its characteristics without a power supply.

Active and Passive components--Comprehensive Knowledge of Passive Devices

From the nature of the circuit, there are two basic features of a passive device:

  • (1) self or consumption of electrical energy, or the conversion of electrical energy into other forms of energy.

  • (2) only the input signal is needed, and it can work normally without the need of the external power supply.

Passive components are mainly resistors, inductors and capacitance components. The common feature is that there is no need to add power in the circuit to work when there is a signal.

And there are also two basic features of a active components:

  • (1) it also consumes electrical energy.

  • (2) in addition to the input signal, it is necessary to have a power supply to work normally.

It can be seen that active devices and passive devices are quite different in terms of working conditions and working modes of circuits, which must be paid much attention in the learning process of electronic technology.Active and passive components PDF: http://ocw.nthu.edu.tw/ocw/upload/12/234/02handout.pdf

V.Types of passive components

Passive components can be divided into circuit and connectors according to the circuit function.

  • (1) Such as diode,resistor,resistor network,capacitor, inductor,transformer,relay,key,speaker and switch.

  • (2) Such as connector,shoket, line and PCB.

Notice: Passive components are mainly resistors, inductors and capacitance components. The common feature is that there is no need to add power in the circuit to work when there is a signal.

 Book Recommendation

  • Passive Electronic Component Handbook 2nd Edition

A reference on electronic components for electronics engineers, designers, and technicians, providing characteristic data, performance curves, and design guidelines essential for selecting optimal components. Material is organized in sections on devices, including resistors, transformers, relays and switches, batteries, overcurrent protective components, and filters, with final sections on connector and interconnection technology, electronic device cooling, and component handling with ESD control. This new edition of the reference has been divided into two volumes on passive and active components. Includes many tables and b&w diagrams. Annotation c. by Book News, Inc., Portland, Or.

--Charles A. Harper (Author)

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