IPC-A-640 Standard: Complete Guide to Optical Fiber Assembly Acceptance

Fiber optic assemblies are unforgiving. Unlike copper wire harnesses where a slightly imperfect crimp might still conduct electricity, a contaminated fiber end face or improper splice can completely block light transmission. There’s no “good enough” with fiber—it either meets spec or it doesn’t work.

That’s why IPC developed IPC-A-640, the acceptance standard specifically for optical fiber, optical cable, and hybrid wiring harness assemblies. While most engineers are familiar with IPC-A-620 for copper wire harnesses, IPC-A-640 addresses the unique inspection and acceptance challenges that fiber optics present: microscopic contamination, precise connector geometry, fusion splice quality, and bend radius requirements that don’t apply to copper.

I’ve worked with both standards, and the transition from copper to fiber optic assemblies requires a different mindset. You can’t visually inspect a fiber end face with the naked eye—you need specialized equipment and training. This guide covers what you need to know about IPC-A-640: the class system, key acceptance criteria, inspection requirements, and how it relates to other IPC standards.

What is IPC-A-640?

IPC-A-640, officially titled “Acceptance Requirements for Optical Fiber, Optical Cable, and Hybrid Wiring Harness Assemblies,” provides acceptance criteria for cable and wire harness assemblies that incorporate optical fiber technology. The standard was developed by IPC (Association Connecting Electronics Industries) to fill a gap that IPC-A-620 couldn’t address—the specialized requirements of fiber optic communications systems.

The standard covers fiber optic communications systems (FOCS) including single-mode and multimode fibers, various connector types, fusion and mechanical splices, and hybrid assemblies that combine optical fiber with traditional copper wiring.

IPC-A-640 Revision History

Revision	Release Date	Key Updates
Original	July 2017	First release, companion to IPC-D-640
Revision A	April 2022	Current revision, updated acceptance criteria, enhanced illustrations

The current revision is IPC-A-640A, released in April 2022. This standard is relatively new compared to established standards like IPC-A-610 or IPC-A-620, reflecting the more recent widespread adoption of fiber optics in aerospace, military, telecommunications, and industrial applications.

What IPC-A-640 Covers

The standard provides acceptance requirements for:

Optical Components:

• Fiber optic connectors (SC, LC, ST, FC, MTP/MPO, and others)
• Fusion splices and mechanical splices
• Optical transceivers and active devices
• Passive optical components (couplers, splitters, attenuators)

Cable and Harness Assembly:

• Fiber cable preparation and termination
• Strength member attachment
• Strain relief and boot installation
• Cable routing and bend radius control
• Bundling fiber within wire harnesses

Inspection and Testing:

• End face inspection criteria
• Visual acceptance requirements
• Optical testing (insertion loss, return loss)
• Documentation and traceability

What IPC-A-640 Does NOT Cover

Understanding the standard’s boundaries prevents misapplication:

• Detailed test procedures — The standard references test methods but doesn’t provide step-by-step procedures
• In-service acceptance — Criteria are for new assemblies, not aged or field-used hardware
• Design requirements — That’s covered by IPC-D-640
• Copper wire harness assemblies — Use IPC-A-620 for non-fiber wiring
• PCB assembly acceptance — Use IPC-A-610 for populated circuit boards

IPC-A-640 Performance Classes Explained

Like other IPC acceptance standards, IPC-A-640 uses a three-class system to establish different levels of acceptance criteria based on the end-use application. The class system recognizes that a fiber optic assembly for a consumer device doesn’t need the same rigor as one destined for a spacecraft.

Class Definitions

Class 1 — General Electronic Products Products where basic functionality is the primary requirement. Cosmetic imperfections are acceptable if the assembly functions within specifications. Limited life expectancy is typical.

Class 2 — Dedicated Service Electronic Products Products requiring extended life and continuous performance. Uninterrupted service is desired but not critical. Higher workmanship standards than Class 1.

Class 3 — High-Performance / High-Reliability Electronic Products Products where continued high performance is critical and equipment downtime cannot be tolerated. End-use environments may be harsh. Most stringent acceptance criteria apply.

Space / Military / Hazardous Applications IPC-A-640A includes an Appendix A that defines additional requirements beyond Class 3 for space flight, military systems, and hazardous environment applications. These address unique concerns like outgassing, extreme thermal cycling, and radiation exposure.

IPC-A-640 Class Comparison

Aspect	Class 1	Class 2	Class 3
Primary Focus	Function	Extended Life	Continuous Reliability
End Face Cleanliness	Basic	Moderate	Stringent
Connector Geometry	Wider tolerance	Moderate	Tightest tolerance
Splice Loss Limits	Relaxed	Standard	Most demanding
Documentation	Basic	Standard	Comprehensive
Inspection Frequency	Sample	Higher sample or 100%	100% typical
Typical Industries	Consumer, basic industrial	Telecom, commercial	Aerospace, medical, military

Selecting the Appropriate Class

The customer or user specifies the class—not the manufacturer. If no class is specified in the contract, clarify before production begins. Defaulting to Class 2 may not be appropriate for fiber optic assemblies given the critical nature of optical performance.

Class 1 Applications:

• Consumer fiber optic devices
• Non-critical data links
• Prototype or evaluation assemblies
• Short-life industrial equipment

Class 2 Applications:

• Commercial telecommunications
• Enterprise networking equipment
• Industrial automation systems
• Broadcast and AV equipment
• General medical equipment (non-life-critical)

Class 3 Applications:

• Aerospace flight systems
• Military communications and weapons systems
• Medical life-support equipment
• Submarine and undersea systems
• Space flight hardware
• Nuclear facility controls

Key IPC-A-640 Acceptance Criteria

Fiber optic acceptance differs fundamentally from copper wire inspection. While copper crimps and solder joints are evaluated visually, fiber optic performance depends on microscopic conditions at the connector end face and within splices that require specialized inspection equipment.

Connector End Face Inspection

The end face is where light couples between fibers. Contamination, scratches, or geometry problems here directly cause signal loss. IPC-A-640 defines acceptance criteria for end face conditions.

End Face Zones:

Fiber optic connector end faces are divided into zones for inspection purposes:

Zone	Description	Importance
Core Zone (Zone A)	The light-carrying center of the fiber	Most critical — defects here directly affect signal
Cladding Zone (Zone B)	Surrounding the core	Important for multimode, affects beam quality
Adhesive/Epoxy Zone (Zone C)	Ferrule-to-fiber bond area	Contamination can migrate to core
Contact Zone (Zone D)	Ferrule mating surface	Affects physical contact and geometry

Contamination Acceptance Criteria:

Defect Type	Class 1	Class 2	Class 3
Particles in Core Zone	Not allowed	Not allowed	Not allowed
Particles in Cladding Zone	Limited size	Smaller limit	Minimal
Scratches through Core	Not allowed	Not allowed	Not allowed
Surface scratches (not through core)	Limited	More limited	Most limited
Contamination in Contact Zone	Allowed with limits	More restricted	Most restricted

The specific dimensional limits vary by fiber type (single-mode vs. multimode) and connector style. Always reference the current revision of IPC-A-640 for exact specifications.

Connector Geometry Requirements

Beyond cleanliness, connector geometry affects mating performance. Key parameters include:

Ferrule End Face Geometry:

Parameter	Definition	Why It Matters
Radius of Curvature	Spherical polish radius	Ensures proper physical contact between mated connectors
Apex Offset	Distance from fiber core to sphere apex	Affects contact pressure distribution
Fiber Height/Protrusion	Fiber position relative to ferrule	Prevents air gap or fiber damage
Angle (for APC connectors)	Angled polish for return loss	Critical for high-return-loss applications

Geometry is typically measured with an interferometer, not visual inspection. IPC-A-640 references industry standards like IEC 61300 series for specific measurement methods and limits.

Fusion Splice Acceptance Criteria

Fusion splicing permanently joins two fibers by melting the ends together. IPC-A-640 provides visual acceptance criteria for fusion splices.

Acceptable Fusion Splice Characteristics:

• Smooth, uniform splice region
• No visible bubbles, inclusions, or voids
• Fiber cores aligned (verified by loss measurement)
• Protective sleeve properly applied and centered

Fusion Splice Defects:

Defect	Description	Acceptance
Bubbles/Voids	Air trapped in splice region	Defect all classes
Core offset	Visible misalignment of fiber cores	Defect if exceeds loss spec
Diameter mismatch	Visible difference in fiber diameters	Process indicator or defect depending on severity
Contamination	Particles or debris in splice	Defect all classes
Incomplete fusion	Fibers not fully joined	Defect all classes
Excessive bulge	Splice diameter significantly larger than fiber	Process indicator or defect depending on class

Splice loss (measured in dB) is the ultimate acceptance criterion. Visual inspection identifies obvious defects, but optical testing confirms performance.

Mechanical Splice Acceptance Criteria

Mechanical splices use alignment mechanisms rather than fusion to join fibers. They’re field-installable but typically have higher loss than fusion splices.

Acceptable Mechanical Splice Characteristics:

• Index-matching gel properly distributed
• Fibers fully inserted to stops
• Locking mechanism properly engaged
• No fiber damage visible

Bend Radius Requirements

Fiber optic cables have minimum bend radius requirements to prevent signal loss and fiber breakage. Bending fiber too tightly causes macrobend loss (light escapes the core) and can permanently damage the fiber.

Typical Bend Radius Requirements:

Fiber/Cable Type	Minimum Bend Radius (Static)	Minimum Bend Radius (Dynamic/Installation)
Standard single-mode fiber	15-25 mm	30-50 mm
Bend-insensitive single-mode	5-10 mm	10-15 mm
Standard multimode fiber	25-38 mm	50-75 mm
Armored cable	Per manufacturer spec	Usually 10-20x cable OD
Ribbon cable	Per manufacturer spec	Usually larger than individual fiber

IPC-A-640 requires compliance with manufacturer specifications and includes acceptance criteria for routing, cable ties, and support hardware that affect bend radius.

Cable and Harness Assembly Criteria

Strain Relief:

• Boot properly installed and positioned
• No exposed fiber at cable-to-connector transition
• Strain relief device (if used) properly secured

Strength Member Termination:

• Aramid yarn or other strength members properly dressed and secured
• No loose or protruding fibers
• Termination method per manufacturer specification

Cable Jacket:

• No cuts, nicks, or damage exposing internal components
• Proper strip length at terminations
• Marking and labeling legible and correct

Read more IPC Standards:

IPC-A-640 vs IPC-A-620: Understanding the Difference

Engineers familiar with IPC-A-620 for copper wire harnesses often ask how IPC-A-640 differs. While both are acceptance standards for cable assemblies, they address fundamentally different technologies.

Comparison Table: IPC-A-640 vs IPC-A-620

Aspect	IPC-A-640	IPC-A-620
Scope	Optical fiber and hybrid assemblies	Copper wire and cable assemblies
Termination Focus	Connector end faces, splices	Crimps, soldering, IDC
Primary Concerns	Light transmission, contamination, geometry	Electrical continuity, mechanical strength
Inspection Equipment	Fiber scope, interferometer, OTDR	Visual, microscope, pull testing
Test Methods	Optical loss, return loss	Continuity, hi-pot, pull force
Current Revision	Revision A (April 2022)	Revision E (October 2022)
Companion Standard	IPC-D-640 (design)	IPC-D-620 (not published, design in A-620)

When to Use Each Standard

Use IPC-A-640 when:

• Assembly contains optical fiber (any amount)
• Hybrid assemblies with fiber and copper
• Fiber optic communications systems
• Optical sensor cables

Use IPC-A-620 when:

• Pure copper wire harness assemblies
• No optical fiber present
• Traditional electrical interconnects

Use Both when:

• Complex assemblies with separate fiber and copper sections
• Apply IPC-A-640 to fiber portions, IPC-A-620 to copper portions

IPC-A-640 vs IPC-D-640: Acceptance vs Design

IPC-A-640 and IPC-D-640 are companion documents—one covers design requirements, the other covers acceptance criteria.

Standard	IPC-D-640	IPC-A-640
Title	Design and Critical Process Requirements	Acceptance Requirements
Focus	How to design fiber optic assemblies	How to inspect finished assemblies
Content	Materials, processes, documentation	Visual criteria, test requirements
Primary Users	Design engineers, process engineers	Inspectors, quality engineers
Released	2016	2017 (Rev A: 2022)

IPC-D-640 tells you how to design the assembly correctly. IPC-A-640 tells you how to verify the finished product meets requirements. Using both ensures a complete quality system for fiber optic assemblies.

Inspection Equipment for IPC-A-640 Compliance

Unlike copper wire inspection where visual examination often suffices, fiber optic inspection requires specialized equipment.

Essential Inspection Equipment

Equipment	Purpose	Typical Use
Fiber Inspection Scope	View connector end faces	Contamination, damage inspection
Video Inspection Probe	Display end face on monitor	Training, documentation, detailed analysis
Interferometer	Measure connector geometry	Radius, apex offset, fiber height
Optical Power Meter	Measure light power	Loss testing, system verification
Light Source	Provide test signal	Used with power meter for loss measurement
OTDR	Locate faults, measure loss/length	Splice verification, troubleshooting
Visual Fault Locator	Visible red light through fiber	Continuity check, break location

Magnification Requirements

IPC-A-640A specifies magnification requirements based on what’s being inspected:

Inspection Task	Minimum Magnification
General cable/harness visual	1X – 4X
Connector body, ferrule	4X – 10X
End face (initial)	100X – 200X
End face (detailed)	200X – 400X
Fusion splice	40X – 100X

Testing Requirements in IPC-A-640

Visual inspection alone cannot verify fiber optic performance. IPC-A-640 requires optical testing to confirm assemblies meet specifications.

Optical Test Parameters

Parameter	Definition	Typical Spec (varies by application)
Insertion Loss (IL)	Light lost through connector or splice	0.1 – 0.5 dB per connector
Return Loss (RL)	Light reflected back toward source	> 45 dB (UPC), > 65 dB (APC)
Link Loss	Total loss through complete assembly	Per link loss budget

Test Conditions

IPC-A-640A references standard test conditions from industry specifications:

Standard Test Conditions:

• Temperature: 23°C ± 5°C
• Humidity: 45% – 75% RH

Extended Test Conditions (for Class 3 and Space/Military applications):

• Temperature cycling
• Vibration testing
• Humidity exposure
• Additional environmental tests per contract

Implementing IPC-A-640 in Your Facility

Successfully implementing IPC-A-640 requires training, equipment, and documented procedures.

Step 1: Assess Current Capabilities

Evaluate your facility against IPC-A-640 requirements:

• Do you have proper inspection equipment?
• Are technicians trained in fiber optic handling?
• Do procedures address fiber-specific requirements?

Step 2: Obtain Training

While IPC doesn’t currently offer a dedicated IPC-A-640 certification program like they do for IPC-A-610 or IPC-A-620, training options include:

• Manufacturer training (connector, equipment, and fiber vendors)
• FOA (Fiber Optic Association) certification programs
• In-house training using IPC-A-640 as the reference
• ETA International fiber optic certifications

Step 3: Acquire Equipment

Minimum equipment for IPC-A-640 compliance:

• Fiber inspection scope (handheld or bench)
• Optical power meter and light source
• Cleaning supplies (lint-free wipes, appropriate solvents)
• Proper fiber handling tools

Step 4: Develop Procedures

Create work instructions that reference IPC-A-640 for:

• Incoming inspection of fiber components
• In-process inspection during assembly
• Final acceptance testing
• Nonconformance handling
• Documentation and traceability

Step 5: Integrate with Quality System

Link IPC-A-640 to your quality management system:

• Reference in quality manual
• Include in supplier requirements
• Use for customer quality agreements
• Document in process control plans

IPC-A-640 Resources and Where to Purchase

Where to Buy IPC-A-640

Source	URL	Notes
IPC Official Store	shop.ipc.org	PDF and hardcopy available
ANSI Webstore	webstore.ansi.org	Electronic format
Document Center	document-center.com	Authorized dealer
IHS Markit	global.ihs.com	Standards subscription available
Accuris (Techstreet)	store.accuristech.com	Electronic and print

Current pricing is approximately $200-350 depending on format and membership status. IPC members receive discounts.

Related IPC Standards

Standard	Title	Relationship
IPC-D-640	Design and Critical Process Requirements for Optical Fiber, Optical Cable and Hybrid Wiring	Companion design standard
IPC-A-620	Requirements and Acceptance for Cable and Wire Harness Assemblies	Copper wire harness acceptance
IPC-A-610	Acceptability of Electronic Assemblies	PCB assembly acceptance
IPC-HDBK-640	Guidelines for Optical Fiber, Optical Cable, Hybrid Wiring	Supplementary handbook

Other Useful Resources

Industry Standards:

• IEC 61300 series — Fiber optic interconnecting devices and passive components
• TIA-455 series (FOTP) — Fiber optic test procedures
• TIA-568 — Commercial building telecommunications cabling

Training and Certification:

• Fiber Optic Association (FOA) — thefoa.org
• ETA International — eta-i.org
• Connector and equipment manufacturer training programs

Reference Materials:

• IPC-A-640A includes Excel spreadsheet verification and validation checklist
• Color illustrations showing acceptable and defect conditions

Frequently Asked Questions About IPC-A-640

Is IPC-A-640 certification available like IPC-A-610 or IPC-A-620?

Currently, IPC does not offer a dedicated certification program for IPC-A-640 comparable to the CIS/CIT programs for IPC-A-610 or IPC-A-620. However, IPC may develop certification in the future as fiber optic assembly becomes more prevalent. In the meantime, companies typically use manufacturer training, FOA certification, or internal training programs with IPC-A-640 as the reference document. Always check with IPC for the latest training offerings.

How does IPC-A-640 address hybrid assemblies with both fiber and copper?

IPC-A-640 covers the fiber optic portions of hybrid assemblies. For the copper wire portions, IPC-A-620 applies. When building hybrid assemblies, apply each standard to its respective technology. The standards are designed to work together—there’s no conflict in requirements. Your work instructions should clearly identify which standard governs each portion of the assembly.

What’s the relationship between IPC-A-640 and IPC-D-640?

IPC-D-640 is the design standard; IPC-A-640 is the acceptance standard. Think of IPC-D-640 as telling you how to design and build fiber optic assemblies correctly, while IPC-A-640 tells you how to inspect and accept the finished product. They’re companion documents—using both provides complete coverage from design through acceptance. IPC-D-640 was released in 2016, followed by IPC-A-640 in 2017.

Can I use IPC-A-640 for field-installed fiber optic assemblies?

IPC-A-640 defines acceptance criteria for “new/beginning of life” hardware—assemblies as manufactured. The standard explicitly states it’s not intended to define “in service” acceptance criteria for hardware degraded by aging or use. For field installations, IPC-A-640 criteria can be applied to newly installed connectors and splices, but degradation assessment of existing fiber infrastructure may require different criteria agreed upon between user and supplier.

What inspection equipment do I need at minimum for IPC-A-640 compliance?

At minimum, you need a fiber inspection scope (at least 200X magnification for end face inspection), optical power meter with appropriate light source for loss testing, and proper cleaning supplies. For production environments, video inspection probes that display on monitors are preferred for documentation and training. If you’re verifying connector geometry (radius of curvature, apex offset), an interferometer is required. The specific equipment needs depend on your class requirements and the types of fiber assemblies you produce.

Conclusion

IPC-A-640 fills a critical need for fiber optic assembly acceptance criteria. As fiber optics expand into more applications—data centers, aerospace, autonomous vehicles, 5G infrastructure, and medical devices—having a standardized acceptance document becomes increasingly important.

The standard’s class system provides appropriate rigor for different applications, from consumer products to space flight hardware. Its companion relationship with IPC-D-640 creates a complete framework for fiber optic assembly quality, from design through final acceptance.

If your organization works with fiber optic assemblies and hasn’t yet adopted IPC-A-640, now is the time. The standard provides objective acceptance criteria that eliminate ambiguity, reduce disputes, and ensure consistent quality. Combined with proper training and equipment, IPC-A-640 gives your quality system the foundation it needs for fiber optic excellence.

For organizations already using IPC-A-620 for copper wire harnesses, IPC-A-640 is the natural extension when fiber optics enter your product mix. The class system and documentation philosophy are similar—the technical requirements simply address the unique challenges of optical technology.

Fiber optics aren’t going away. If anything, bandwidth demands and EMI considerations are driving more applications toward optical solutions. Having your quality system ready with IPC-A-640 positions your organization for this optical future.