Allied Telesis AT-QSFP28-1CU 100G DAC PASSIVE 1M 100G DAC PASSIVE 1M

Product Overview

The Allied Telesis AT-QSFP28-1CU is a 100G QSFP28 passive Direct Attach Copper (DAC) cable with a fixed 1-meter length, designed for short-reach 100 Gigabit Ethernet connections within a rack or between adjacent racks. Unlike optical transceivers, this passive copper cable requires no additional SFP28 or QSFP28 modules — the QSFP28 connectors are factory-terminated to the cable assembly, reducing cost and eliminating optical component failure points. It is compatible with all Allied Telesis products featuring QSFP28 ports and interoperable with third-party QSFP28-compliant switches and routers.

Product Description

The Allied Telesis 100G QSFP28 DAC passive 1m direct attach cable (AT-QSFP28-1CU) is the cost-effective solution for 100 Gigabit intra-rack and short inter-rack connectivity. DAC cables are passive copper assemblies: there are no optical lasers, no transceivers, and no active electronic components inside the cable. The electrical signal travels directly over twinaxial copper wire between two QSFP28 ports. This makes DAC cables significantly less expensive than QSFP28 optical transceivers (such as QSFP28-SR4 or QSFP28-LR4), while delivering identical 100G bandwidth at distances up to 1 meter. The tradeoff is range: DAC cables are only suitable for connections within the same rack or to an immediately adjacent rack. For longer distances — across a data center row, between rows, or between buildings — optical solutions are required. The AT-QSFP28-1CU is ideal for switch-to-switch stacking connections, server-to-ToR switch uplinks, and storage interconnects in high-density data center deployments. Available from authorized Allied Telesis resellers including Creation Networks.

Key Features

• 100G QSFP28 to QSFP28 — Full 100 Gigabit Ethernet throughput on both ends
• Passive DAC Construction — No optical components, no active electronics; lower cost and higher reliability than optical
• 1-Meter Fixed Length — Designed for intra-rack and adjacent-rack connections only
• No Separate Transceivers Required — QSFP28 connectors are factory-integrated into the cable assembly
• Compatible with All QSFP28 Products — Works with Allied Telesis QSFP28-equipped switches, routers, and line cards
• Low Power Consumption — Passive design draws minimal power from the host port

Typical Applications

• Top-of-rack (ToR) switch to server 100G uplinks within the same rack
• Switch-to-switch 100G stacking or interconnect within a single rack
• Storage array to switch 100G connections in hyper-converged infrastructure
• Data center spine-leaf fabric interconnects within adjacent racks
• High-frequency trading and low-latency computing environments requiring passive copper (no SFP signal conversion latency)

Technical Specifications

Frequently Asked Questions

Q: What is the difference between a DAC cable and a QSFP28 optical transceiver?

A DAC (Direct Attach Copper) cable is a passive copper assembly with integrated QSFP28 connectors. An optical transceiver (such as QSFP28-SR4 or QSFP28-LR4) is a pluggable module that converts electrical signals to optical signals for transmission over fiber. DAC cables are cheaper and have no active components, but are limited to short distances (typically 1–3 meters for passive, up to 7 meters for active). Optical transceivers support distances from 100m (SR4 multimode) to 10km+ (LR4 single-mode).

Q: Why choose passive DAC over active DAC?

Passive DAC cables have no electronic components inside, making them more reliable (no failure modes from active circuitry) and lower power. Active DAC cables use signal conditioning electronics to extend range to 5–7 meters. For 1-meter connections, passive is always preferred.

Q: Can I use the AT-QSFP28-1CU with non-Allied Telesis switches?

Yes, provided the other device uses a QSFP28 port and complies with QSFP28 MSA standards. Interoperability is generally broad, but confirm with your switch vendor if in doubt.

Q: Is 1 meter enough for my rack?

1 meter is appropriate for connecting two devices within the same rack or between two immediately adjacent rack units. If the distance exceeds approximately 1 meter, use a longer passive DAC (if available) or an optical solution.

Q: Does this cable require any configuration?

No. Passive DAC cables are plug-and-play. Insert both QSFP28 connectors and the link comes up automatically once both ends are seated in active ports. No drivers or configuration are required.