1、_ SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising there
2、from, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions. Copyright 2010 SAE International All rights reserved. No part of this publication m
3、ay be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-4970 (outside U
4、SA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/AIR6113 AEROSPACE INFORMATION REPORT AIR6113 Issued 2010-12 Superseding AS5603 Guidelines for
5、 Design of Digital Fiber Optic Link Loss Budget Methodology RATIONALE This document was originally published as AS5603, “Digital Fiber Optic Link Loss Budget Methodology for Aerospace Platforms”. A revised standard, AS5603A, will be released in the future, providing the specification details for a f
6、iber optic link budget in a form that is more suitable for use as an industry standard. This new document, AIR6113, is intended to archive the information that existed in the original AS5603 document. INTRODUCTION This SAE document provides specific process and procedure based on broadly accepted en
7、gineering practices for the establishment of link loss power budgets in aerospace digital fiber optic systems. The underlying purpose is to improve the process of aerospace digital fiber optic link architecture, specification, and interface developments by promoting a standard terminology and method
8、ology across the industry. A communication facilitation tool such as this streamlines the development of system requirements, establishes high-level confidence in predicted performance, and communicates to component suppliers the quality and quantity of test data needed to support high performance f
9、iber optic links. 1. SCOPE This document draws from, summarizes, and explains existing broadly accepted engineering best practices. This document defines the process and procedure for application of various best practice methods. This document is specifically intended as a standard for the engineeri
10、ng practice of development and execution of a link loss power budget for a general aerospace system related digital fiber optic link. It is not intended to specify the values associated with specific categories or implementations of digital fiber optic links. This document is intended to address bot
11、h existing digital fiber optic link technology and accommodate new and emerging technologies. The proper application of various calculation methods is provided to determine link loss power budget(s), that depend on differing requirements on aerospace programs. A list of parameters is provided as gui
12、dance for aerospace fiber optics applications along with a check list to help assure that appropriate parameters and impairments have been accounted for in the link budget. SAE AIR6113 Page 2 of 99 1.1 Approach The general approach of this document is to outline existing industry best practices for
13、link budget analysis, including specific reference to MIL-STD-2052A Ref. 22. Additionally, reference is made to existing component and link test procedures, test data, and best practices commonly used to support the link loss power budget. Where industry best practices are not well established, appr
14、opriate alternative methods are described. 1.2 Data Basis and Methodology Link loss power budgets are ultimately tied to component test and qualification data. The quality, quantity and pedigree of component test and qualification results that exist can impact the approach and methodology used for d
15、evelopment of a link loss power budget. Accuracy of statistical methods depends on the quality of the statistical data available. Furthermore, technology maturity of a component can affect the methodology used. As such, various link loss budget methodologies are discussed with reference to the quali
16、ty of data available. Additionally, the Technology Readiness Level (TRL) Refs. 2,3 of components is discussed along with the influence it can have on link budget analysis. A range of possible cases of component maturity and corresponding data exists. For example, flight qualified components may exis
17、t, without a large statistical database to help quantify probability and confidence. Similarly, high quality and quantity statistical data may exist for some components, but these components may not have been through system flight-testing. Often, commercial components exist with minimum specificatio
18、ns and thus are neither flight qualified nor have a statistical database to draw on for analysis. These different cases suggest different approaches or at least different confidence and possibly margin associated with the link budget analysis. Various analysis methods exist for establishing and anal
19、yzing link budgets (discussed in Section 4). As mentioned previously, the quality of the link budget analysis, and the resulting allocations, are dependent on the quality of the component loss and performance test data that are utilized. This translates directly to the confidence in predicted system
20、 performance. While different approaches provide differing levels of accuracy, they also may drive the component testing that is performed. In some cases, system developments must take on the burden of additional component testing to generate the quality of test data needed and to avoid even more co
21、stly over-design margin. 1.3 Link Loss Power Budget Background and Overview The Power Budgeting is a part of the Systems Engineering Process. It is not an isolated analysis. It must be a consistent part of the overall systems engineering approach. This standard provides the different analyses as a t
22、ool for the customers and the link designers to evaluate the fiber technologies in meeting the fiber optics systems application intent/purpose. The Figure 1 diagram provides a visual relationship of systems engineering process and power budgeting. The key emphasis is that an understanding of the rel
23、ationships between the different considerations and their effects on each other and on the power budget is critical. These tools provide a means to either evaluate the current fiber link performance in certain environmental conditions (operational conditions, maintenance concept, etc.) or could be u
24、sed to set performance requirements based on critical fiber link application needs. They serve as metrics to better understand how the link design will perform for the life of the system from beginning of life, installation, and end of life. Link loss power budgets generally begin with the light sou
25、rce (laser or Light Emitting Diode, LED) output power, P, and extend through a power at the input to the receivers, R. The source power level is typically limited by the available appropriate products. The power level available from a source must account for environmental variations and end-of-life
26、(EOL) degradation at a minimum. SAE AIR6113 Page 3 of 99 FIGURE 1 - SYSTEMS ENGINEERING PROCESS AND POWER BUDGETING The required optical signal power at the receiver end of the link must be established by defining a required sensitivity referenced to some measure of performance, such as required lin
27、k Bit Error Ratio (BER). There are other important receiver parameters related to the input signal such as dynamic range and clock timing jitter tolerance which must be included in performance analysis. Receiver sensitivity, however, is the driving limitation of most digital fiber optic links and co
28、rresponding link loss power budgets, and can be defined to incorporate many other receiver related effects and signal impairments. In between the optical transmitter source and the receiver are the transport and distribution media and elements for the link. This includes the fiber, connectors, and a
29、ll the passive and active components that make up the link. Each of these elements has a loss, L, associated with it that makes up the overall link loss. In addition to link loss, there are other impacts or adjustments, La, that contribute to degradation of link performance. A list and definition of
30、 these parameters is provided in the following major section. In addition to the standard adjustments applied to loss in aerospace links, newer technologies can bring additional adjustments or complexities. Several technologies used primarily in the long haul terrestrial domain are starting to be co
31、nsidered for aerospace fiber optic data and communications links. Optical amplification and wavelength division multiplexing (WDM) are two such technologies. They both are primarily used with single mode optical fiber, which is now being considered more seriously for aerospace environments, partly b
32、ecause it provides access to these new technologies. Forward error correction (FEC) and electronic dispersion compensation (EDC) are two more technologies of import. They are well suited for direct application to multimode fiber links as well as single mode. These two technologies enhance the effect
33、ive sensitivity of receivers and can often be treated as an adjustment to receiver sensitivity in a link loss budget. In general, these technologies bring additional complications to link loss budget analysis. Optical amplifiers complicate standard single mode link loss techniques in several ways. L
34、ink loss, L, may be compensated for by link gain, G, but at a cost of increased noise. This increase in noise degrades the performance of a receiver at a given input optical signal power. For links with optical gain, optical loss becomes secondary to the resulting optical signal to noise ratio (OSNR
35、). Implications of this for the link loss budget will be discussed in more detail in following sections. The implications are applicable to single mode or multimode. However, in multimode format the mode dependent spontaneous noise is sufficiently detrimental that no successful multimode optical amp
36、lifier products are currently in use. This is thus considered only a single-mode technology. SAE AIR6113 Page 4 of 99 For WDM based links, link budgets must be viewed on a wavelength basis. Performance of many optical components varies with wavelength, and thus there is a spectral loss penalty. This
37、 can be addressed in several ways, such as by maintaining a spectral loss penalty for each component or by providing a budget at multiple wavelengths. While WDM has been predominantly a single mode technology, Coarse WDM (CWDM) is gaining popularity and being examined for multimode aerospace applica
38、tions. The growing applicability of these originally single-mode technologies, in addition to other advancements in technologies, methodologies, and standards, is part of the motivation for the creation of this document. As such, an attempt is made to both pull together the known industry best pract
39、ices and incorporate implications of newer technologies to aerospace fiber optic digital links. 2. APPLICABLE DOCUMENTS The following publications form a part of this document to the extent specified herein. The latest issue of SAE publications shall apply. The applicable issue of the other publicat
40、ions shall be the issue in effect on the date of the purchase order. In the event of conflict between the text of this document and references cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exe
41、mption has been obtained. Applicable and reference documents are listed in the References section of this report. 3. DEFINITIONS OF GENERAL FIBER OPTIC LINK TERMS AND PARAMETERS WITH RELEVANT UNITS The following listed parameters and terms, with associated definitions and explanations, are most rele
42、vant to the formulation of a link loss budget. Definitions for fiber optic terms used in this standard are in accordance with ANSI/TIA-440-B-2004, “Fiber Optic Terminology” Ref. 3, except where specifically defined. Some terminology defined in ANSI/TIA-440-B-2004 is further explained here with speci
43、fic emphasis on link budget relevance or impact. This list of parameters is intended to help assure common standard terminology and to be a reminder of parameters of most importance. It is intended to be thorough, though there is no claim that it is comprehensive. 3.1 Definition of General Fiber Opt
44、ic Link Terms 3.1.1 Link I/O Terminology Definitions and Units Input/Output (I/O) includes transmitters and receivers in addition to optical modulators and amplifiers, since they are often lumped with transmitter and receiver I/O devices. Power is specified in Watts or dBm. The dBm, and correspondin
45、g dB fractional loss, is most typical since loss budgets are comprised of cascaded products of power losses, which become sums of losses in logarithmic dB representation. Units are highlighted by unit designator brackets, e.g., dB. 3.1.1.1 BER: Bit Error Ratio (or Rate) is that measure of bit errors
46、 per total bits transmitted at some specified point in the link. BER is often measured with a pseudo random bit pattern generator prior to the transmitter and an error analyzer at the receiver. A receivers optical average power sensitivity is defined at a particular BER. Many standards exist, but BE
47、R = 10-10and BER = 10-12are typical specified values for modern telecommunications links that support data links (e.g., ITU-T G.957, G.826). 3.1.1.2 Dynamic Range dB: Dynamic Range typically refers to the power range ratio, measured in dB, of the transmitter, receiver, or system over which specified
48、 performance is met. It is usually limited by receiver sensitivity on the low end, and maximum transmitter output or receiver saturation on the high end. A valid links power budget must fall within the dynamic range, and the margin is the measure of how far from the limits the link is. SAE AIR6113 P
49、age 5 of 99 3.1.1.3 Electromagnetic Interference (EMI) Disruption of Receiver: A fiber optic receiver includes an optical detector, which typically produces relatively low current levels before amplification. Therefore, this is a circuit point susceptible to EMI disruption. A common source of such corruption is the conducted interference resulting from a co-located transmitter. EMI impact is sometimes accounted for by add
copyright@ 2008-2019 麦多课文库（www.mydoc123.com）网站版权所有
备案/许可证编号：苏ICP备17064731号-1