Chinese name:Insertion loss
English name: insertion loss
Definition:Some devices or branch circuit (filter, impedance matching unit, etc.) in a circuit, energy loss or gain.
Subject:Communications technology (level 1 subject); Communication principle and basic technology (secondary discipline)
Insertion loss refers to somewhere in transmission system due to the insert of components or devices of the load power loss, it is expressed as the element or device inserted before the load on the received power and after inserting the same load receives the power ratio in decibels.
1. insertion loss is refers to between transmitter and receiver, and insert the cable or element, signal loss usually refers to failure. Insertion loss to receive a signal level corresponding decibels (dB).More than
2. insertion loss refers to the power loss, failure is refers to the relative amplitude signal voltage the original signal amplitude is smaller. Such as for an ideal lossless transformer Deputy ideal transformer lossless, namely the insertion loss is zero. The concept of general use in the filter insertion loss, said the use of the filter and not before using the signal power loss.Channel insertion loss refers to the output port of the output optical power and the ratio of the input port input optical power, is an unit with the dB. Insertion loss is associated with the input wavelength, are also associated with switch state. Is defined as: L = - 10 l0g (Po/Pi)Type:
Pi - light power input to the input port, the unit for mw;
Po - - from the output port receives the light power, the unit for mw.
For OLP, concrete can be divided into the sender receiver of insertion loss and insertion loss.
Return loss
Chinese name:Return loss
English name: return loss
defineReflection coefficient inverse mode. Usually expressed in decibels.
Belongs to the disciplineCommunications technology (level 1 subject); Communication principle and basic technology (secondary discipline)
Return loss, also known as the reflection loss. Is the cable link due to impedance mismatch of reflection, is a line of its own reflection. Mismatch occurs mainly in the connector, but may also occur in cable characteristic impedance change takes place, so the quality of construction is the key to improve the return loss. Return loss will introduce signal fluctuations, the returned signal will be duplex gigabit network as the signal is received and confusion.
Basic introduction
Return loss: in the high frequency occasions, reflect the travelling wave protection equipment "transition" is reflected proportion, under this parameter can be directly measured, the protection device and a system of flood wave impedance matching degreeReturn loss, return loss. Return loss is said signal reflection performance parameters. Return loss suggests that part of the incident power is reflected back to the source. For example, if the injection (DBM) 0 1 mw power to the amplifier with 10% is reflected back (rebound), return loss is 10 db. From mathematical perspective, return loss for - 10 1 gPower) (incident power). Return loss usually specified in the input and output.It refers to the optical fiber connection, after to the reflected light to the input end (continuous transmission of scattering light) relative to the ratio of input light decibels, the greater the return loss is better, to reduce the effect of reflected light on the light source and system.Usually require reflected power as small as possible, so that will have more power to the load. Typically the designer's goal is to at least 10 db return loss. Sometimes in order to get better noise coefficient, IP3 or system gain cannot meet this "thumb" 10 db return loss.As far as possible the optical fiber end face processed into spherical or oblique sphere is an effective method of improving return loss.How to improve the digital cable return loss (RL) indicators:
Return loss index profile
Return loss is an important index for digital cable products, return loss to merge the two kinds of the effects of reflection, including deviation of nominal impedance (such as: 1002) as well as the structure, used for characterization of the performance of the link or channel. It is due to the cable length on the characteristic impedance of the inhomogeneity, in the final analysis is caused by the inhomogeneity of cable structure. Due to signal reflection caused by different locations in the cable to the signal at the receiving end is equivalent to the multipath effect in the transmission in wireless channels, that cause the signal's time spread and frequency selective fading, diffusion time lead to pulse broadening, make the receiver signal pulse overlap but cannot. Signal in the cable also leads to the multiple reflection in the signal power attenuation, affect the signal-to-noise ratio at the receiving end, lead to the increase of the bit error rate, and thus limit the transmission speed. In the process of production of digital cable, cable prone to unqualified return loss index.
The measures of enhancing return loss
Efforts to improve the return loss (RL) has the following three:.
(1) improve the concentricityThe insulation series production process, the diameter of the copper conductor tolerance within + 0.002 mm, insulation outside diameter deviation within + / - 0.01 mm. Concentricity is above 96%, and the surface is smooth and rounded. Otherwise, the single wire in the ground for the characteristic impedance of the cable will appear over index of larger peak.
(2) composite technology
By a certain percentage of "pre-twist" or "twisted" technology and cooperate with the cross use plastic skeletonBy a certain percentage of "pre-twist" or "twisted" technology can eliminate the influence of single wire insulation eccentricity of characteristic impedance and at the same time can reduce the requirement of single wire insulation concentricity. And cross plastic skeleton, can maintain the stability of the cable structure that caused the change of the characteristic impedance of single non-uniform becomes smooth, make its proximal crosstalk and return loss at high frequency performance is quite good.
As we all know, the line of the two wire center distance (S) of fluctuations can cause line of impedance. Inevitable, owing to the eccentricity of the single wire insulation layer insulation line of impedance showed some degree of cyclical change, in a number of local length remains the same, the total length of a ladder shaped by high and low volatility, line of segments of impedance different uneven long, these uneven long or short or long, when less than 1/8 of the cable use frequency corresponding to the wavelength, close to half wave impedance changes will be "perceived by the marching of electromagnetic wave" caused by the electromagnetic wave reflection, part of the reflection stacked up together, due to phase falling impedance fluctuation, return loss and generate additional loss (failure on a frequency curve Peak). With the increase of frequency, wave length decreases, and will make more uneven long
Through the line of "pre-twist" or "to back twist, make the line to the distance between the conductor S to complete a cycle change the length of the corresponding contains several ground on the pitch, but not more than cable use frequency of the highest wavelength, the line of impedance in a pitch also completed a period of rapid change, the size of sinusoid wave, so that the impedance of the line the total length of change becomes smooth, reflection no longer occur, the uniformity of the line on the impedance changes greatly. In addition to cooperate with cross plastic skeleton, maintain the stability of the cable structure, make the single non-uniform caused the change of characteristic impedance is smooth.Through the above measures can make the digital cable near end crosstalk and return loss at high frequency performance is quite good.
(3) used for adhesion line technology
Adhesion line of technology refers to using two extrusion molding machine, a machine head co-extrusion, will sync with a line of two insulated wire extrusion to be bonded together. After ground adhesion between the lines, to ensure the ground line structure stability, keep line center distance of two wire (S) stability to improve the uniformity of impedance, thus improve the return loss indicator;Also can avoid insulated conductor after bending twisting conductor loose core and affect the return loss of the cable.Datang telecom super five, six cable production now, the related measures, can make the product return loss index reached a quite high level.
