Operating Segments and Geographic Information - Information on Reportable Segments (Details) $ in Millions	3 Months Ended		6 Months Ended
	Dec. 29, 2018 USD ($)	Dec. 30, 2017 USD ($)	Dec. 29, 2018 USD ($) segment	Dec. 30, 2017 USD ($)
Information on reportable segments
Number of broad business categories (in segment) | segment			2
Total net revenue	$ 306.9	$ 205.4	$ 575.4	$ 396.3
Gross profit	$ 178.0	$ 119.4	$ 328.4	$ 232.1
Gross margin (as a percent)	58.00%	58.10%	57.10%	58.60%
Operating income	$ 32.9	$ 6.9	$ 31.7	$ 13.6
Operating margin (as a percent)	10.70%	3.40%	5.50%	3.40%
Other Items
Information on reportable segments
Total net revenue	$ 0.0	$ 0.0	$ 0.0	$ 0.0
Gross profit	(9.8)	(6.3)	(20.0)	(12.6)
Operating income	(31.0)	(21.7)	(76.0)	(41.1)
Network and Service Enablement | Segment Measures
Information on reportable segments
Total net revenue	223.7	157.2	414.4	293.7
Gross profit	$ 146.0	$ 99.5	$ 267.2	$ 187.1
Gross margin (as a percent)	65.30%	63.30%	64.50%	63.70%
Operating income	$ 32.8	$ 11.2	$ 49.2	$ 15.1
Operating margin (as a percent)	14.70%	7.10%	11.90%	5.10%
Network and Service Enablement | Network Enablement | Segment Measures
Information on reportable segments
Total net revenue	$ 195.5	$ 122.0	$ 360.0	$ 233.6
Gross profit	$ 125.7	$ 74.4	$ 228.6	$ 144.7
Gross margin (as a percent)	64.30%	61.00%	63.50%	61.90%
Network and Service Enablement | Service Enablement | Segment Measures
Information on reportable segments
Total net revenue	$ 28.2	$ 35.2	$ 54.4	$ 60.1
Gross profit	$ 20.3	$ 25.1	$ 38.6	$ 42.4
Gross margin (as a percent)	72.00%	71.30%	71.00%	70.50%
Optical Security and Performance Products | Segment Measures
Information on reportable segments
Total net revenue	$ 83.2	$ 48.2	$ 161.0	$ 102.6
Gross profit	$ 41.8	$ 26.2	$ 81.2	$ 57.6
Gross margin (as a percent)	50.20%	54.40%	50.40%	56.10%
Operating income	$ 31.1	$ 17.4	$ 58.5	$ 39.6
Operating margin (as a percent)	37.40%	36.10%	36.30%	38.60%
Product
Information on reportable segments
Total net revenue	$ 272.8	$ 181.3	$ 513.9	$ 346.4
Product | Other Items
Information on reportable segments
Total net revenue	0.0	0.0	0.0	0.0
Product | Network and Service Enablement | Segment Measures
Information on reportable segments
Total net revenue	189.8	133.6	353.3	245.0
Product | Network and Service Enablement | Network Enablement | Segment Measures
Information on reportable segments
Total net revenue	176.0	114.5	325.9	217.3
Product | Network and Service Enablement | Service Enablement | Segment Measures
Information on reportable segments
Total net revenue	13.8	19.1	27.4	27.7
Product | Optical Security and Performance Products | Segment Measures
Information on reportable segments
Total net revenue	83.0	47.7	160.6	101.4
Service
Information on reportable segments
Total net revenue	34.1	24.1	61.5	49.9
Service | Other Items
Information on reportable segments
Total net revenue	0.0	0.0	0.0	0.0
Service | Network and Service Enablement | Segment Measures
Information on reportable segments
Total net revenue	33.9	23.6	61.1	48.7
Service | Network and Service Enablement | Network Enablement | Segment Measures
Information on reportable segments
Total net revenue	19.5	7.5	34.1	16.3
Service | Network and Service Enablement | Service Enablement | Segment Measures
Information on reportable segments
Total net revenue	14.4	16.1	27.0	32.4
Service | Optical Security and Performance Products | Segment Measures
Information on reportable segments
Total net revenue	$ 0.2	$ 0.5	$ 0.4	$ 1.2