Can modules be hot-swapped in the Keysight 8166A mainframe?

No. The mainframe must be powered down before inserting or removing any of the optical modules.

Do the E8401A and E8408A mainframes have built-in GPIB or LAN interfaces?

No, these mainframes do not have built-in communication interfaces on the chassis. System control and communication interfaces are determined entirely by the VXI Slot 0 controller card installed in the mainframe.

What is the primary difference in optical module support between the 8164B and 8166A?

The 8164B features a dedicated slot (Slot 1) specifically for single- or dual-width Tunable Laser Sources (TLS) plus four standard module slots. The 8166A provides 17 standard slots for optical sources, power meters, and attenuators, but does not feature the dedicated back-loading tunable laser slot structure found on the 8164B.

Keysight Technologies (Agilent HP) Mainframes

8 models with full specifications in Mainframes.

Keysight Technologies (formerly Agilent HP) offers two primary architectures in its modular mainframe catalog: the 816x series Lightwave Measurement systems and the E-series VXIbus systems. These mainframes serve as the structural, power, and communication foundation for multi-channel optical component testing and high-density automated test systems. Choosing the correct mainframe depends on the technology platform (optical modules vs. VXI cards), the required slot capacity, and the specific power or communication interface needs of your test environment.

Max Lightwave Slots: 17 slots (8166A)
Max VXI Slots: 13 slots (E1401B, E8401A)
Lightwave Interfaces: GPIB, LAN, USB, RS-232, VGA
VXI Module Support: C-size cards

All models

Model	Type	Dimensions (W×H×D)	Display	Interfaces
8164A	Mainframes	426 x 145 x 545	Color active LCD, 600 x 400 points visible	GPIB, RS-232C, Parallel (Centronics), VGA
8164B	Mainframes	426 mm x 177 mm x 545 mm	6.4-inch Color TFT LCD, 640 x 480 VGA resolution	GPIB (IEEE 488.2), LAN (10/100 Base-T), USB 2.0 (Host & Device), VGA Video Output
E1401B	Mainframes	483 mm × 352 mm × 631 mm (with rack flanges)	Front panel status LEDs (+5V, -5.2V, +12V, -12V, +24V, -24V, -2V, Fan, Temp, Access)	25-pin D-sub diagnostic/monitoring connector on rear panel
8166A	Mainframes	426 mm × 177 mm × 535 mm	Backlit LCD display for status monitoring	GPIB (IEEE-488.2), RS-232 (serial), Centronics (parallel), Trigger I/O (BNC)
E8401A	Mainframes	424.5 mm × 352 mm × 631 mm	None (LED status indicators only)	None (external communication interface is provided by the installed VXI Slot 0 controller)
E8408A	Mainframes	213 mm × 222 mm × 561 mm	None (status LEDs only)	None (determined by Slot 0 controller card)
E5250A	Mainframes	426 mm × 132.5 mm × 448 mm	20-character x 2-line Vacuum Fluorescent Display (VFD)	GPIB (IEEE-488)
E8403A	Mainframes	424.5 mm × 352 mm × 631 mm	Front panel LED status indicators (SYSFAIL, AC, TEMP, FAN)	Rear panel diagnostic connector

Lightwave Measurement Mainframes

The 816x series mainframes are designed specifically for optical testing, accommodating tunable lasers, power sensors, optical heads, return loss modules, and attenuators.

8164A & 8164B: These benchtop units support five total slots. This includes one slot dedicated to back-loadable tunable laser modules (supporting single- or dual-width TLS modules on the 8164B) and four slots for front-loadable compact modules or power sensors. While the 8164A offers GPIB, RS-232C, and parallel interfaces with a 600 x 400 LCD, the newer 8164B upgrades connectivity to include LAN (10/100 Base-T) and USB 2.0 (Host and Device) alongside a 6.4-inch color TFT display at 640 x 480 resolution.
8166A: For high-port-count applications, this 4U rackmount system provides 17 standard slots for optical modules. Unlike the smaller mainframes, modules in the 8166A are not hot-swappable; the system must be powered down before modules are inserted or removed. It features backplane-routed trigger lines accessible by all 17 slots.

VXI C-Size Modular Mainframes

For automated testing outside the dedicated optical domain, Keysight offers high-reliability VXI mainframes that comply with VXIbus Revision 1.4 for C-size modules.

E8408A: A compact, 4-slot mainframe designed for portable or small-scale applications. It features a half-rack footprint and provides 324 W of usable power at 55 °C, with standard status LEDs rather than a built-in display screen.
E8401A: A larger 13-slot, 8U mainframe that provides up to 500 W of usable power. It relies on an impeller fan design for efficient cooling and features LED status indicators on the front panel.
E1401B: A robust 13-slot, 8U mainframe designed for high-density configurations requiring superior power supply serviceability. It features a rear-removable power supply design with a Mean Time to Repair (MTTR) of under 5 minutes and delivers up to 1500 VA of maximum input power. Solid-state automatic daisy-chain jumper connections are used for VMEbus BG/IACK lines.